Low-Flux Converting Process for PGM Collector Alloy

ABSTRACT

A low-flux converting process for PGM collector alloy. The process includes feed introduction into a molten alloy pool, oxygen injection into the pool, tapping the slag, and tapping the PGM-enriched alloy. The collector alloy contains no less than 0.5 wt % PGM, 40 wt % iron, and 0.5 wt % nickel. If added flux material contains more than 10 wt % silica and 10 wt % CaO/MgO, the feed contains no more than 20 parts by weight added flux per hundred collector alloy. The process can also include using a refractory protectant in the converter; melting partially pre-oxidized collector alloy to form the initial molten alloy pool; magnetic separation of slag; recycling part of the slag to the converter; smelting catalyst material in a primary furnace to produce the collector alloy; and/or smelting the converter slag in a secondary furnace with slag from the primary furnace.

CROSS-REFERENCE TO RELATED APPLICATION

None.

BACKGROUND OF THE INVENTION

The platinum group metals, i.e., ruthenium, rhodium, palladium, osmium,iridium, and platinum (“PGM”), are often recovered from used catalystmaterials such as, for example, automotive catalytic converters. Thecatalyst materials are smelted in a furnace, typically with a fluxmaterial such as CaO, and the PGM are preferentially collected in analloy pool below the slag. While the PGM are dilute in the furnace slag,nevertheless these losses can be significant due to the high volume ofslag and a general inability to economically recover the dilute values.The PGM collector alloys may contain up to 12 wt % PGM, and usuallycontain more than 40 wt % iron. Enrichment is necessary if a higher PGMcontent is desired.

PGM enrichment of iron-rich, sulfide-lean collector alloy bypyrometallurgical converting was disclosed in S. D. McCullough,“Pyrometallurgical iron removal from a PGM-containing alloy,” ThirdInternational Platinum Conference ‘Platinum in Transformation,’ TheSouthern African Institute of Mining and Metallurgy (2008). PGMenrichment of sulfur-free or low-sulfur (<1 wt %) PGM collector alloywas more recently proposed in patent documents U.S. Pat. No. 10,202,669B2 and US 2018/0142330 A1. The PGM-enriched alloys generally contain arelatively high proportion of iron (>10 wt %).

There are a number of drawbacks associated with known converters andconverting processes preventing them from being practically implementedto process PGM collector alloy generated from smelting catalystmaterials. The converting process can be relatively slow. In the patentdocuments mentioned above, the collector alloy and slag-formingmaterials were melted for 10 hours prior to oxygen injection. Moreover,the converting process is exothermic, and the rate of oxygen addition isgenerally limited to avoid excessive temperatures. Further, the severeconditions in the converter, especially at high oxygen injection rates,lead to corrosion and short lifespans for refractory lining.

The industry has generally accepted that, similar to smelting,relatively high levels of added flux materials such as SiO₂ and MgO/CaOare needed for the formation of a low melting, light density slag toadequately remove impurities and improve the PGM content of thePGM-enriched alloy product from a converter. For example, theaforementioned patent documents disclose the addition of sulfur- andcopper-free slag-forming material in minimum proportions of 0.2 or 1part by weight per 1 part by weight collector alloy, where theslag-forming materials contain 70-90 wt % SiO₂ and 10-30 wt % MgO/CaO,or 40-90 wt % MgO/CaO and 10-60 wt % SiO₂.

The industry needs technology that can address one or more of theshortcomings of conventional converting processes for PGM collectoralloys. Such technology would desirably achieve one or more of thefollowing: improve the alloy melting rate, oxygen addition rate, and/orthe processing rate or capacity of the converter; provide lower levelsof iron and/or deleterious materials in the PGM-enriched collectoralloy; reduce PGM losses in converter slag; improve reliability and/ordurability of converter components; reduce converter maintenancerequirements and/or operating interruptions; and/or improve theefficiency and practicality of using converters incorporated as part ofan overall process to recover and enrich PGM collector alloy, e.g., fromcatalyst or other PGM-containing materials.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

The present disclosure is directed to a converting process forrecovering platinum group metals (“PGM”) that addresses drawbacks ofknown converting processes. Applicant has observed that the high levelsof added flux materials comprising more than 10 wt % CaO/MgO and 10 wt %SiO₂ in known PGM collector alloy converting processes can be reduced oravoided in the converting processes disclosed herein, and that limitingthe amount of such flux in this manner leads to a reduced volume ofconverter slag, reduced alloy melting time, and increases convertingcapacity and/or throughput.

Applicant has also observed that a relatively small amount of refractoryprotectant can be added after melting the alloy pool to inhibitrefractory corrosion and extend refractory life, and that furnace slagfrom smelting catalyst material can be conveniently used as theprotectant. Additionally, applicant has observed that partiallypre-oxidizing a portion (or all) of the collector alloy for the initialmelt and/or converter feed can further reduce the time periods requiredfor melting the initial alloy pool and converting the collector alloy.Further, applicant has observed that recycling a portion of theconverter slag to the converter between cycles also provides a way toreduce PGM losses; and that high-grade slag can be selectively recoveredfor recycling to the converter, e.g., by magnetic separation of theconverter slag. Moreover, recycling the slag in this manner can returnreadily reducible pre-oxidized metal values such as nickel to theconverter, and thus effectively increase oxygen addition rates.

Applicant has further found that the converter can be integrated into anoverall PGM recovery process by smelting catalyst material in a primaryfurnace to produce the collector alloy and/or by smelting the converterslag in a secondary furnace with slag from the primary furnace. The slagfrom either of the furnaces, preferably from the primary furnace, can beused as refractory protectant.

In one aspect of the present invention, embodiments provide a processfor converting platinum group metal (PGM) collector alloy, comprisingthe steps of: (a) introducing a converter feed into a pot of a converterholding a molten alloy pool; (b) injecting oxygen-containing gas intothe alloy pool to convert iron and one or more other oxidizable elementsfrom the collector alloy to corresponding oxides and enrich PGM in thealloy pool; (c) allowing a slag comprising the iron oxide to collect ina low-density layer above the alloy pool; (d) tapping the low-densitylayer to recover the slag from the converter; and (e) tapping the alloypool to recover the PGM-enriched alloy.

The converter feed preferably comprises a collector alloy comprising noless than 0.5 wt % PGM, no less than 40 wt % iron, and no less than 0.5wt % nickel, based on the total weight of the collector alloy. Theprocess enables conversion with low added flux, such as less than 20parts by weight of the added flux material per 100 parts by weightcollector alloy, including no added flux material. An added fluxmaterial in the converter feed is optional, but if it is used andcomprises both more than 10 weight percent silica and more than 10weight percent of calcium oxide, magnesium oxide, or a combination ofcalcium oxide and magnesium oxide, by weight of the added flux material,then the converter feed preferably comprises no more than 20 parts byweight of the added flux material per 100 parts by weight collectoralloy, more preferably no more than 15 parts by weight of the added fluxmaterial per 100 parts by weight collector alloy, and especially no morethan 10 parts by weight of the added flux material per 100 parts byweight collector alloy.

In any embodiment, the process can further comprise lining the pot witha refractory material; and supplying a refractory protectant to the potholding the alloy pool. The refractory protectant can be supplied at arate up to 20 parts by weight refractory protectant per hundred parts byweight of the collector alloy in the converter feed. Preferably, therefractory protectant is added at a rate not more than 18 parts byweight per 100 parts by weight of the collector alloy, more preferablyat a rate between 5 and 15 parts by weight refractory protectant per 100parts by weight of the collector alloy. The refractory protectantpreferably comprises a component in common with the refractory material.Alumina is a preferred component in common.

In any embodiment, the process can comprise jacketing the pot andcirculating a coolant, preferably an aqueous coolant, e.g., water and/orwater/glycol, through the jacket, especially during oxygen-containinggas injection in step (b). In any embodiment, the process can includemonitoring refractory lining temperature, preferably by sensingtemperature in the refractory lining with one or more sensors mounted inthe refractory lining, communicating temperature sensing informationfrom the one or more sensors to one or more transmitters, andtransmitting signals containing the temperature sensing information fromthe one or more transmitters to a receiver. The one or more transmittersare preferably mounted externally on the pot and wirelessly transmit thesignals to the receiver.

In any embodiment, the process can further comprise, prior to step (a),the step of: (I) partially pre-oxidizing a portion of the collectoralloy. Preferably, the partial pre-oxidation in step (I) comprises from10 to 90 percent conversion of iron, more preferably from 25 to 75percent iron conversion, and even more preferably from 30 to 60 percentiron conversion, based on the iron in the collector alloy portion priorto step (I). In any embodiment, the process can further comprise thesteps of: (II) melting the partially pre-oxidized collector alloy in thepot to form a sufficient volume of the alloy pool for the injection ofthe oxygen-containing gas in step (b); and (III) then commencing theconverter feed introduction into the pot in step (a) and theoxygen-containing gas injection into the alloy pool in step (b). Theslag is optionally wholly or partially separated from the partiallypre-oxidized collector alloy prior to step (II), but is preferablysupplied with the partially pre-oxidized collector alloy to the pot formelting in step (II).

In any embodiment, the converting process can further comprise the stepsof: (A.1) separating the slag recovered in step (d) into a plurality ofportions; (A.2) recycling at least one of the recovered slag portionsfrom step (A.1) to the converter feed introduced to the pot in step (a),wherein the converter feed comprises the recycled slag in an amount offrom about 5 to 100 parts by weight per 100 parts by weight of thecollector alloy, preferably wherein the converter feed comprises therecycled slag in an amount of from 10 to 50 parts by weight per 100parts by weight of the collector alloy. For example, the slag recoveredfrom one operating cycle of the converter can be cooled, solidified,comminuted, and recycled in a subsequent operating cycle. The separationstep (A.1) preferably comprises separation into a high grade fractionhaving a relatively high PGM content for recycle and a low gradefraction, e.g., magnetic separation and recycling the magneticallysusceptible fraction, and/or recycling all or part of the slag recoveredfrom a final slag tapping regardless of magnetic susceptibility.

In any embodiment, the converting process can comprise the steps of:(C.1) prior to steps (a) to (e), beginning a converter operation cycleby melting a partially pre-oxidized collector alloy in the pot to formthe alloy pool; (C.2) then, prior to step (e), repeating a sequence ofsteps (a), (b), (c), and (d) a plurality of times, wherein step (d) ineach sequence follows steps (b) and (c); (C.3) recycling the slagrecovered from a final tapping of the low-density layer in step (d) in alast one of the sequences of step (C.2) to the converter feed in step(A.2) regardless of magnetic susceptibility, and/or recycling all orpart of a non-magnetically susceptible fraction separated from the finaltapping in step (d) to the converter feed in step (A.2); and (C.4) afterthe final tapping of the low-density layer in step (d) in a last one ofthe sequences of step (C.2), tapping the alloy pool in step (e).Preferably, for the tapping(s) of the low-density layer preceding thefinal tapping, alloy entrained in the low-density layer is allowed tosubstantially settle into the alloy pool before the tapping of therespective low-density layer(s). For the final tapping, the low densitylayer is tapped quickly to avoid freezing and alloy may optionally beentrained in the low-density layer.

In any embodiment, the process can further comprise the steps of: (E.1)smelting a catalyst material in a primary furnace; (E.2) recovering aprimary furnace slag and a first collector alloy from the primaryfurnace; (E.3) smelting the primary furnace slag in a secondary furnace;(E.4) recovering a secondary furnace slag and a second collector alloyfrom the secondary furnace; (E.5) supplying the first and secondcollector alloys to converter feed in step (a); and (E.6) supplying atleast a portion of the slag recovered from the converter in step (d) tothe secondary furnace for smelting with the primary furnace slag in step(E.3).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified schematic process flow diagram of a converterprocess according to embodiments of the present invention.

FIG. 1B is a simplified schematic flow diagram of a PGM recovery processintegrating the converter of FIG. 1A according to embodiments of thepresent invention.

FIG. 1C is a schematic block flow diagram of a PGM recovery processemploying partial pre-oxidation of a collector alloy according toembodiments of the present invention.

FIG. 1D is a schematic block flow diagram of an exemplary starter alloypreparation procedure according to embodiments of the present invention.

FIG. 2A is a simplified side view of a top blown rotary converter (TBRC)pot according to embodiments of the present invention.

FIG. 2B is a simplified side sectional view of the TBRC pot of FIG. 2A.

FIG. 2C is a simplified side sectional view of the TBRC pot of FIG. 2Bshowing flame pre-oxidation prior to the start of a converter cycleaccording to embodiments of the present invention.

FIG. 3 is a simplified side view of a TBRC pot partially cut away toshow the molten alloy pool at the beginning of a fill in a convertercycle according to embodiments of the present invention.

FIG. 4 shows the TBRC pot of FIG. 3 partially filled with alloy and slagearly in a converter cycle.

FIG. 5 schematically shows the alloy and slag in the pot of FIG. 4 atthe end of an oxygen injection cycle in the converter cycle.

FIG. 6 schematically shows the alloy and slag in the pot of FIG. 5following alloy disentrainment from the slag layer prior to a non-finalslag tapping in the converter cycle.

FIG. 7 schematically shows the alloy and slag in the pot of FIG. 4 justprior to the final slag tapping in the converter cycle.

FIG. 8 schematically shows a simplified process flow diagram of a PGMrecovery process according to embodiments of the present invention.

FIG. 9 is a schematic block flow diagram of a PGM recovery processemploying a converter and a finishing furnace according to embodimentsof the present invention.

FIG. 10 is a schematic block flow diagram of a PGM recovery processemploying a refractory-lined converter and refractory protectantaccording to embodiments of the present invention.

FIG. 11 is a schematic block flow diagram of a PGM recovery processemploying a partially pre-oxidized PGM collector alloy according toembodiments of the present invention.

FIG. 12 is a schematic block flow diagram of a PGM recovery processemploying a converter, converter slag recycle to the converter and anoptional finishing furnace according to embodiments of the presentinvention.

FIG. 13 is a schematic block flow diagram of a PGM recovery processemploying a converter, magnetic separation of converter slag, andconverter slag recycle to the converter according to embodiments of thepresent invention.

FIG. 14 is a schematic block flow diagram of a PGM recovery processemploying a converter, alloy disentrainment prior to non-final slagtapping, a final slag tapping without complete alloy disentrainment, andoptional recycle of the final slag tapping to the converter according toembodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout the entire specification, including the claims, the followingterms shall have the indicated meanings.

An “added” material as used herein in reference to a process refers toan imported ingredient or component that is added as an additionalingredient or component supplementary to that which is already presentin the process.

The term “and/or” refers to both the inclusive “and” case and theexclusive “or” case, and such term is used herein for brevity. Forexample, a composition comprising “A and/or B” may comprise A alone, Balone, or both A and B.

The term “alloy” refers to a substance having metallic properties andbeing composed of two or more chemical elements of which at least one isa metal.

The term “catalyst material” refers to metal on or in a supportmaterial, such as, for example, a metal washcoat on silica, alumina, oranother ceramic, used to increase the rate of a chemical reactionwithout itself undergoing any permanent chemical change. Catalystmaterial can be spent, partially spent, or new, or active or inactive.

The term “collector alloy” refers to an alloy containing dilutequantities of one or more precious metals, which may optionally bepartially oxidized. If the collector alloy is partially oxidized,“collector alloy” also refers to any oxidized material that may bepresent with the alloy. The term “raw collector alloy” refers to acollector alloy from a furnace that is untreated and comprises less than10 wt % of oxides.

The term “comminute” refers to the reduction in average particle size ofa solid material, e.g., by crushing, grinding, milling, cutting,vibrating, and so on.

The term “converter” refers to an apparatus used to oxidize elements inan alloy; the term “converting” refers to the conversion of oxidizableelements in an alloy to the corresponding oxides, and may be usedinterchangeably with the term “oxidation.”

The term “feed” as used herein refers to any reactant, reagent, diluent,additive, and/or other component supplied to a reactor or other vesselduring the process.

The term “flux” is used in its metallurgical sense to refer to amaterial added to a meltable or molten material to facilitate theagglomeration, separation, and removal of undesirable substances, likesand, ash, or dirt. For purposes of this invention, the term “flux” isspecifically limited to materials comprising more than 10 weight percentsilica and more than 10 weight percent of calcium oxide, magnesiumoxide, or a combination of calcium oxide and magnesium oxide, by weightof the flux material.

The term “in” refers to a first material or component that is within,on, or adjacent to a second material or component.

A “jacket” refers to a cavity external to a vessel for heat exchangebetween a fluid circulating through the jacket and the walls of thevessel. The jacket can be a shell creating an annular space around thevessel, a half-pipe coil jacket, a dimple jacket, plate coils, and soon.

The term “lance” refers to a pipe for supplying oxygen to a furnace,flame, or another high temperature area or region.

As used herein, “mesh size” refers to the US Standard Sieve Series where“−” indicates passing through and “+” indicates retained on.

The term “metal” refers to an opaque lustrous elemental chemicalsubstance that is a good conductor of heat and electricity and, whenpolished, a good reflector of light.

The term “metallic” refers to a metal or another substance with theproperties of a metal.

The term “pot” refers to a vessel for holding a molten material.

The “partial pre-oxidation” refers to conversion of some but not all,e.g., up to 90 percent by weight, of the oxidizable species in an alloyin a separate step prior to a main converting step.

The term “protectant” refers to a substance that provides protection.

The term “recovering” as used herein refers to the collection orisolation of a material.

The term “recycling” as used herein refers to returning a materialalready present in a cyclic process to a previous stage in the process;“recycle” refers to the material recycled.

The term “refractory” refers to a substance that is resistant to heat. A“ramming refractory” is one that is applied as a mix of aggregate,powder, binder, and/or other additives, and compacted using a rammingmethod, e.g., with an air rammer or masonry hammer.

The term “slag” refers to the oxidized material separated from metalsand/or alloys during smelting or refining. “High grade slag” refers to aslag having a relatively higher PGM content than a “low grade slag.” Forpurposes herein, “high grade slag” has a PGM concentration of greaterthan 800 ppm, e.g., greater than 1000 ppm PGM, and “low grade slag” hasa PGM concentration of less than or equal to about 800 ppm. For example,slag having a 2000-3000 ppm PGM content is a high grade slag withrespect to a low grade slag with 800 ppm PGM. High grade slag preferablycomprises no less than 2000 ppm PGM.

The term “smelting” refers to the extraction of metal from a materialsuch as an ore by a process involving heating and melting.

The term “tapping” refers to the act of causing a fluid to flow from apipe or container.

A “top blown rotary converter” or “TBRC” refers to a converter that canblow or inject a gas from above into or onto a molten phase in arotatable pot.

According to embodiments of the present invention, a process forconverting platinum group metal (PGM) collector alloy comprises thesteps of: (a) introducing a converter feed into a pot of a converterholding a molten alloy pool, wherein the converter feed comprises: (i)100 parts by weight of a collector alloy comprising no less than 0.5 wt% PGM, no less than 40 wt % iron, and no less than 0.5 wt % nickel,based on the total weight of the collector alloy; and (ii) if an addedflux material comprises more than 10 weight percent silica and more than10 weight percent of calcium oxide, magnesium oxide, or a combination ofcalcium oxide and magnesium oxide, by weight of the added flux material,no more than 20 parts by weight of the added flux material; (b)injecting oxygen-containing gas into the alloy pool to convert iron andone or more other oxidizable elements from the collector alloy tocorresponding oxides and enrich PGM in the alloy pool; (c) allowing aslag comprising the iron oxide to collect in a low-density layer abovethe alloy pool; (d) tapping the low-density layer to recover the slagfrom the converter; and (e) tapping the alloy pool to recover thePGM-enriched alloy.

In any embodiment, the process can further comprise lining the pot witha refractory material; and supplying a refractory protectant to the potholding the alloy pool at a rate not more than 20 parts by weight of thecollector alloy, preferably no more than 18 parts by weight per 100parts by weight of the collector alloy, more preferably at a ratebetween 5 and 15 parts by weight refractory protectant per 100 parts byweight of the collector alloy. In any embodiment, the refractoryprotectant can be supplied to the pot (i) after initially melting thealloy pool and prior to commencing step (b), (ii) during one or both ofsteps (a) and (b), and/or (iii) after stopping one or both of steps (a)and (b) to tap the low-density layer in step (d), prior to resuming saidone or both of steps (a) and (b). The refractory protectant can besupplied to the pot together with the collector alloy introduced in step(a), or preferably is supplied to the pot separately from the collectoralloy introduced in step (a), more preferably wherein the supply ofrefractory protectant to the pot is periodic.

The refractory protectant preferably comprises a component in commonwith the refractory material, such as alumina, for example. In anyembodiment, the process can further comprise injecting theoxygen-containing gas into the alloy pool in step (b) through a lanceextended into the alloy pool, wherein the lance comprises a consumablerefractory material and is advanced into the pool as a tip of the lanceis consumed. The consumable refractory material preferably comprises acomponent in common with the lining, preferably wherein the component incommon comprises alumina. In any embodiment, the refractory material ofthe lining can comprise a ramming refractory comprising alumina,preferably wherein the ramming refractory comprises at least 90 wt %alumina.

In any embodiment, the process can further comprise sensing temperaturein the refractory lining with radially spaced sensors mounted in therefractory lining; communicating temperature sensing information fromthe sensors to one or more transmitters; and transmitting signalscontaining the temperature sensing information from the one or moretransmitters to a receiver. Preferably, the one or more transmitters aremounted externally on the pot and wirelessly transmit the signals to thereceiver.

In any embodiment, the process can further comprise jacketing the potand circulating a coolant, preferably an aqueous heat transfer medium,e.g., water/ethylene glycol/propylene glycol, and the like, through thejacket during step (b).

In any embodiment, the oxygen-containing gas can be injected into theconverter alloy pool at a sufficient rate to maintain the alloy pool ina molten state at a temperature no higher than 1800° C., preferably at atemperature in a range from about 1250° C. to 1700° C., more preferably1450° C. to 1700° C.

In any embodiment, the process can further comprise, prior to step (a),the step of: (I) partially pre-oxidizing a portion of the collectoralloy from a raw state. Preferably, the partial pre-oxidation in step(I) comprises from 10 to 90 percent conversion of iron, more preferablyfrom 25 to 75 percent iron conversion, and even more preferably from 30to 60 percent iron conversion, based on the iron in the collector alloyportion prior to step (I). The collector alloy can be pre-oxidized bypassing comminuted particles through an oxygen-rich flame; by partiallyconverting the collector alloy and tapping the partially oxidized alloy,e.g., in an earlier converter cycle; by contacting particles of thecollector alloy with an oxygen-containing gas at a temperature of atleast 800° C., for example between 800° C. and 950° C., e.g., in arotary kiln; fluidized bed roaster; and so on.

Preferably, the process can further comprise the steps of: (II) meltingthe partially pre-oxidized collector alloy in the pot to form asufficient volume of the alloy pool for the injection of theoxygen-containing gas in step (b); and (III) then commencing theconverter feed introduction into the pot in step (a) and theoxygen-containing gas injection into the alloy pool in step (b). Asdesired, the oxidized components in the partially pre-oxidized collectoralloy from step (I) may be separated and removed in whole or in partprior to melting in step (II), or they can be allowed to remain in thepartially pre-oxidized collector alloy melted in step (II).

In any embodiment, the pre-oxidizing step can comprise (LA) passingcomminuted collector alloy (e.g., a mesh size from about −16, preferably−18 to +200) through an oxygen-rich flame, preferably wherein the flameexhibits a flame temperature of not less than 2000° C., more preferably2000° C. to 3500° C., and especially 2000° C. to 2800° C. The oxygenrich flame is preferably produced by a burner for heating the pot, andthe process can further comprise (LB) depositing at least partiallymelted collector alloy particles from the flame into the pot. Preferablythe process comprises (LC) cooling and solidifying the particles to forma coating of the pre-oxidized collector alloy on an interior surface ofa refractory lining of the pot, e.g., where step (II) comprises meltingthe coating. In this pre-oxidizing procedure the oxidized components inthe partially pre-oxidized collector alloy from step (I) are preferablyallowed to remain in the partially pre-oxidized collector alloy meltedin step (II).

In any embodiment, the pre-oxidizing step can comprise operating theconverter through a pre-oxidation cycle of steps (II), (III), (a), (b),(c), (d), and (e) to prepare a partially oxidized starter alloy, where apartially pre-oxidized collector alloy from an earlier cycle ispreferably melted in step (II) and the alloy recovered from step (e) isused as the partially pre-oxidized starter. The starter alloypreparation cycle can further comprise melting a previously preparedcharge of the partially oxidized starter alloy in the emptied pot toform the alloy pool; periodically or continuously supplying theconverter feed to the alloy pool in step (a) concurrently with theinjection of the oxygen-containing gas in step (b); continuing theinjection of the oxygen-containing gas to partially oxidize the alloypool, preferably wherein from 10 to 90 percent, more preferably from 25to 75 percent, of iron in the converter feed is oxidized, based on theweight of iron in the converter feed supplied to the converter alloypool; tapping the slag from the converter pot, preferably a plurality oftimes; then recovering and solidifying the partially oxidized alloypool. Preferably the solidified, partially oxidized collector alloy fromthe starter alloy preparation cycle is divided into a plurality ofstarter alloy charges for a like plurality of converter operating cyclesand/or starter alloy preparation cycles.

In this pre-oxidizing converter cycle procedure the oxidized componentsin the partially pre-oxidized collector alloy from step (I) arepreferably separated in step (c) and removed in step (d), and thepartially pre-oxidized collector alloy can be recovered in step (e) ofthe pre-oxidizing cycle, cooled, and solidified prior to step (II). Ifdesired, the slag recovered in step (d) of the pre-oxidizing cycle canbe combined with and/or melted with the partially pre-oxidized alloyfrom step (e) in a subsequent step (I) of a collector alloy convertingor pre-oxidation cycle.

In any embodiment, the pre-oxidizing step can comprise contactingparticles of the collector alloy (e.g., a mesh size from about −16,preferably −18 to +200) with an oxygen-containing gas at a temperatureabove 800° C., e.g., between 800° C. and 950° C., preferably by roastingin a rotary kiln, fluidized bed roaster, or any other roasting mechanismtaking care not to melt and excessively aggregate the particlestogether.

In any embodiment, the process can further comprise the steps of: (A.1)separating the slag recovered in step (d) into a plurality of portions;(A.2) recycling a first one of the recovered slag portions from step(A.1) to the converter feed introduced to the pot in step (a). Theconverter feed preferably comprises the recycled slag in an amount offrom about 5 to 100 parts by weight per 100 parts by weight of thecollector alloy, more preferably from 10 to 50 parts by weight per 100parts by weight of the collector alloy in the converter feed. Theprocess preferably comprises (A.2) combining the collector alloy and therecycle slag for concurrent introduction in the converter feed in step(a), preferably from a single feed unit. The recycled slag in step (A.2)preferably comprises a high-grade portion of the recovered slag fromstep (d), i.e., a higher PGM content than an average overall PGM contentof the recovered slag from step (d), and/or the recycled slag has anickel oxide content greater than about 2 percent by weight of therecycled slag.

In any embodiment, the process can comprise the steps of: (B.1) cooling,solidifying, and comminuting the recovered slag from step (d) (e.g.,crushing to a mesh size of −4.8 mm ( 3/16 in.) may be suitable); (B.2)magnetically separating the crushed slag into a magnetically susceptiblefraction and a non-magnetically susceptible fraction; (B.3) recyclingthe magnetically susceptible fraction to the converter feed in step(A.2); and (B.4) optionally recycling a portion of the non-magneticallysusceptible fraction to the converter feed in step (A.2).

In any embodiment, the process can comprise the steps of: (C.1) prior tosteps (a) to (e), beginning a converter operation cycle by melting apartially pre-oxidized collector alloy in the pot to form the alloypool; (C.2) then, prior to step (e), repeating a sequence of steps (a),(b), (c), and (d) a plurality of times, wherein step (d) in eachsequence follows step (c); and (C.3) after a final tapping of thelow-density layer in step (d) in a last one of the sequences of step(C.2), tapping the alloy pool in step (e). Preferably in a step (C.4)all or part of the slag recovered from the final tapping in step (d) isrecycled to the converter feed in step (A.2) regardless of magneticsusceptibility, and/or all or part of the non-magnetically susceptiblefraction separated in step (B.2) from the final tapping in step (d) isrecycled to the converter feed in step (A.2). The process preferablycomprises the steps of: (D.1) for the tapping(s) of the low-densitylayer preceding the final tapping in step (C.2), allowing alloyentrained in the low-density layer to substantially settle into thealloy pool before the tapping of the respective low-density layer(s);and (D.2) for the final tapping in step (C.2), tapping the low-densitylayer within five minutes, optionally entraining alloy in thelow-density layer.

In any embodiment, the process can comprise the steps of: (E.1) smeltinga catalyst material in a primary furnace, preferably a non-convertingfurnace; (E.2) recovering a primary furnace slag and a first collectoralloy from the primary furnace; (E.3) smelting the primary furnace slagin a secondary furnace, preferably a non-converting furnace; (E.4)recovering a secondary furnace slag and a second collector alloy fromthe secondary furnace; (E.5) supplying the first and second collectoralloys to converter feed in step (a); and (E.6) supplying at least aportion of the slag recovered from the converter in step (d) to thesecondary furnace for smelting with the primary furnace slag in step(E.3). The pot of the converter is preferably lined with a refractorymaterial, and a portion of the primary furnace slag from step (E.2) canbe supplied to the pot as a refractory protectant for steps (a) and (b),preferably at a rate not more than 20 parts by weight of the primaryfurnace slag per 100 parts by weight of the collector alloy, morepreferably 18 parts by weight of the primary furnace slag per 100 partsby weight of the collector alloy, more preferably at a rate between 5and 15 parts by weight of the primary furnace slag per 100 parts byweight of the collector alloy.

In any embodiment, the process can comprise any one or more or all ofthe following: (F.1) the oxygen-containing gas injection in step (b) ispreferably continued until the alloy pool comprises no more than about10 wt % iron, preferably no more than 5 wt % iron; and/or (F.2) thePGM-enriched alloy preferably comprises no less than 25 wt % PGM,preferably from 25 to 60 wt % PGM; (F.3) the PGM-enriched alloypreferably comprises no less than 25 wt % nickel, more preferably from25 to 70 wt % nickel; and/or (F.4) the PGM-enriched alloy preferablycomprises no more than 10 wt % iron; and/or (F.5) the PGM-enriched alloypreferably comprises no more than 2 wt % silicon, no more than 2 wt %phosphorus, no more than 10 wt % copper, and/or no more than 2 wt %sulfur; and/or (F.6) the collector alloy preferably comprises from 0.5to 12 wt % PGM; and/or (F.7) the collector alloy preferably comprises noless than 40 wt % iron, preferably 40 to 80 wt % iron; and/or (F.8) thecollector alloy preferably comprises no less than 0.5 wt % nickel,preferably 1 to 15 wt % nickel; and/or (F.9) the collector alloypreferably comprises no more than 3 wt % sulfur, more preferably 0.1 to3 wt % sulfur; and/or (F.10) the collector alloy preferably comprises:no more than 3 wt % copper, more preferably 0.1 to 3 wt % copper; and/orno more than 2 wt % chromium, preferably 0.1 to 2 wt % chromium; and/orno more than 20 wt % silicon, more preferably 1 to 20 wt % silicon.

With reference to the drawings in which like parts are indicated by likenumerals, FIG. 1A schematically shows a converting process 100A forconverting PGM collector alloy according to embodiments of the presentinvention. A converter feed 116 is introduced into a pot 120 of aconverter 118 holding a molten alloy pool 122. The converter 118 can beany suitable converter for oxidizing the iron and other elements in thefeed 116, e.g., using oxygen in a gas bubbled into the alloy pool fromthe top or side or bottom (not shown), which results in the formation ofa light-density slag phase 128. The converter 118 is preferably a topblown rotary converter (“TBRC”) having an inclined, generallycylindrical pot 120 holding the alloy pool 122 as shown that can berotated by motor 119, e.g., at 1 rotation per hour up to 20 rotationsper minute, e.g., 30 rotations per hour, to facilitate mixing andagitation. The pot 120 is often lined with a refractory material 123.TBRCs are known, for example, from patent document U.S. Pat. No.4,581,064, and they are typically custom-designed and built for specificapplications by a number of engineering firms specializing inmetallurgical processing.

In any embodiment, converter feed 116 can be a collector alloy obtainedfrom smelting catalyst material, including the raw collector alloyand/or a partially pre-oxidized collector alloy, and preferablycomprises no less than 0.5 wt % PGM, for example from 0.5 to 12 wt %; noless than 30 wt % iron, for example from 40 to 80 wt % iron; and no lessthan 0.5 wt % nickel, for example from 1 to 15 wt % nickel, based on thetotal weight of the converter feed 116. The converter feed 116 may alsocomprise at least about 0.1 weight percent of each of copper, sulfur,and chromium; for example, from 0.1 to 3 weight percent copper, from 0.1to 3 weight percent sulfur, and from 0.1 to 2 weight percent chromium,based on the total weight of the converter feed 116. The converter feed116 and/or its components can also comprise up 20 wt % silicon, forexample, from 1 to 20 wt % silicon; and up to 15 wt % phosphorus, forexample from 1 to 15 wt % phosphorus, all based on the weight of theconverter feed 116. Other elements may also be present, usually inamounts up to 5 wt %.

The converter feed 116 may optionally comprise an added flux material,but if the added flux material comprises more than 10 weight percentsilica and more than 10 weight percent of calcium oxide, magnesiumoxide, or a combination of calcium oxide and magnesium oxide, by weightof the added flux material, the converter feed 116 comprises no morethan 20 parts by weight of the added flux material per 100 parts byweight of the collector alloy, more preferably no more than 18 parts byweight of the added flux material per 100 parts by weight of thecollector alloy.

The converter 118 can be provided with a preferably water cooled burnerassembly 117 to melt the alloy pool 122. The alloy pool 122 can beconverter feed 116 and/or a collector alloy, which is preferablyinitially at least partially oxidized or converted, and can becomeincreasingly oxidized or converted as the converting process progressesthrough a cycle of operation.

Oxidant gas such as oxygen 124 is preferably injected into the pot 120via lance 126 as the pot is rotated about a longitudinal axis. Theoxygen converts iron and other oxidizable elements in the alloy pool 122to the corresponding iron and other oxides, e.g., iron to iron oxide,silicon to silica, phosphorus to phosphorous pentoxide, chromium tochromium oxide, copper to copper oxide, titanium to titanium oxide, andso on. The rotation and gas injection provide agitation and mixing asthe iron and other impurities are depleted from the alloy pool 122 byoxidation and collect as a floating, low density layer 128, therebyenriching PGM in the alloy pool 122. The low-density layer 128 is tappedperiodically or continuously and recovered as slag 130, for example,from a tap or by tipping the pot 120. Nickel and PGM are generally notas easily oxidized, and these are enriched in the alloy pool 122 andsimilarly recovered from a tap or by tipping the pot 120 as aPGM-enriched nickel alloy 132, which is often solidified in a mold toform ingots. Slag 130 is often cooled, solidified, comminuted, e.g., bycrushing and/or milling, to facilitate handling. For example, a meshsize of −4 (−4.8 mm, − 3/16 in.) may be suitable.

Preferably, a refractory protectant 138 is supplied to the converter 118in an effective amount. The protectant 138 can retard loss of therefractory material from the lining 123, thus extending the refractorylife and reducing the frequency of replacement of the refractory lining123. The protectant 138 can contain a material common to the refractorylining 123, e.g., alumina where the refractory 123 is alumina-based.Where the refractory 123 is alumina-based, the protectant 138 ispreferably an aluminosilicate that melts at a lower temperature than therefractory, i.e., an aluminosilicate glass, which may conveniently besupplied from the furnace slags 106 and/or 112 (see FIG. 1B), preferablyfrom the primary furnace slag 106, for example, where the slags 106and/or 112 also contain alumina. Where the refractory 123 isalumina-based, the amount of alumina in the protectant 138 shouldpreferably not be less than 10 wt %, and the protectant 138 preferablycomprises alumina in an amount of from 25 to 75 wt %, based on the totalweight of the protectant.

An amount of protectant 138 needed to be effective is typically small inproportion to the converter feed 116. Preferably the protectant is addedat less than 20 wt %, based on the weight of the converter feed 116,e.g., from 1 to 10 wt % of the converter feed. The protectant 138 can beadded continuously, but is preferably added periodically, e.g., onto thetop of the alloy pool 122, following initial melting of the pool, andafter each tapping of the slag 128. Excessive amounts of protectant 138provide limited additional protection and lead to higher volumes of slag130, whereas insufficient protectant 138 leads to higher refractorylosses.

The lance 126 is frequently in a region of high temperature due to theoxygen addition and the exothermic nature of the converting reactions inclose proximity, and is often consumable. Where the lance 126 is made ofa consumable material, such as refractory material in common with thelining 123, for example alumina, it may likewise benefit from therefractory protectant 138. When the lance 126 is consumable, it is oftenadvanced, periodically or continuously, as the tip of the lance isconsumed, to maintain oxygen injection below an upper level of the alloypool 122 and minimize unreacted oxygen escaping from the alloy pool 122and/or slag 128. In general, the rate of oxygen-containing gas injectionis preferably as high as possible to rapidly complete the conversion,but not so high as to exceed the operating temperature limits of theTBRC 118 or as to cause unreacted oxygen to bubble up through the uppersurface of the alloy pool 122 and/or low density layer 128.

FIG. 1B schematically shows a PGM recovery process 100B incorporating aconverter 118, preferably the converter process 100A (see FIG. 1A),according to embodiments of the present invention. The PGM collectoralloy is preferably obtained from smelting a catalyst material 102 inprimary furnace 104. The catalyst material 102 often comprises PGM on orin a support such as silica, alumina, clay, zeolite, cordierite, and thelike, e.g., a washcoat of PGM-containing material on a ceramic support.The catalyst material 102 can be any PGM-containing material such aswaste catalyst, for example, catalytic converters for automotiveexhaust, catalyst from a refinery or chemical process industry, and thelike.

If desired, the catalyst material can be conventionally processed toprepare it for smelting, e.g., by size reduction, removal of deleteriousmaterials and/or inert materials that contain little or no PGM, such asby comminution, chemical treatment, magnetic separation, etc. Patentdocument U.S. Pat. No. 5,279,464, for example, discloses comminution andmagnetic separation of the catalyst material from automotive catalyticconverters.

Smelting catalyst material such as in furnace 104 is well known, anduses a conventional furnace, e.g., a non-converting furnace such as anelectric arc furnace, induction furnace, plasma arc furnace, firedfurnace, and so on. For example, patent document U.S. Pat. No. 5,030,274discloses processing catalyst material in an electric arc furnace torecover PGM, and patent documents U.S. Pat. No. 4,295,881 and WO2014154945A1 disclose smelting of chromite-bearing ores to recover PGM.The catalyst material, often with the addition of slag, flux, orcollector metal, is generally continuously fed and when heated in thefurnace forms slag 106 and a PGM-containing collector alloy. Thecollector alloy is relatively dense compared to the lighter slag, andcollects in an alloy pool 108 below an upper layer of the slag 106.

Slag 106 and collector alloy 108 are recovered, periodically orcontinuously, and often cooled and solidified for further processing.For example, collector alloy 108 is often poured into molds, and slag106 is often granulated, dried in a rotary kiln, and packaged in bags ora suitable container. The slag 106 from the primary furnace 104 cancontain residual PGM, often 1-5 wt % of the PGM in the catalyst material102, and is in turn preferably smelted in a secondary furnace 110, whichcan be a furnace similar to furnace 104, e.g., a non-converting furnacesuch as an electric arc furnace, induction furnace, plasma arc furnace,fired furnace, or the like, with the addition of metallurgical coke. Theslag 112 recovered from furnace 110 is further depleted in PGM, and maybe similarly cooled, solidified, granulated, dried, packaged, etc. Theslag 112 can be disposed of as a byproduct or waste material. The PGMare concentrated and recovered in the collector alloy 114 from thesecondary furnace 110, and poured into molds and solidified in a mannersimilar to the collector alloy 108.

In any embodiment, the first PGM collector alloy 108, the second PGMcollector alloy 114, or preferably both, are introduced as converterfeed 116 to converter 118. The converter 118 shown in FIG. 1B can be anysuitable converter for oxidizing the iron and other elements in the feed116, and preferably comprises the converter 118 as described above inprocess 100A in connection with FIG. 1A. The PGM collector alloys 108,114 are often comminuted, e.g., by crushing and/or milling, and fed tothe converter 118 from a hopper 225 via a vibrating feeder 226 as shownin FIG. 8.

Collector alloy 108 and collector alloy 114, separately and/orcollectively in converter feed 116, preferably comprise no less than 0.5wt % PGM, for example from 0.5 to 12 wt %; no less than 30 wt % iron,for example from 40 to 80 wt % iron; and no less than 0.5 wt % nickel,for example from 1 to 15 wt % nickel, based on the total weight of theconverter feed 116, collector alloy 108, and/or collector alloy 114. Thefirst and/or second collector alloys 108, 114, may also comprise atleast about 0.1 weight percent of each of copper, sulfur, and chromium;for example, from 0.1 to 3 weight percent copper, from 0.1 to 3 weightpercent sulfur, and from 0.1 to 2 weight percent chromium, based on thetotal weight of the first and/or second collector alloys. The converterfeed 116 and/or its components can also comprise up 20 wt % silicon, forexample, from 1 to 20 wt % silicon; and up to 15 wt % phosphorus, forexample from 1 to 15 wt % phosphorus, all based on the weight of thePGM-enriched nickel alloy. Other elements may also be present, usuallyin amounts up to 5 wt %.

Slag 130 from the converter 118 is often cooled, solidified, comminuted,e.g., by crushing and/or milling, to facilitate handling. Nickel and PGMare generally not as easily oxidized, and these are enriched in thealloy pool 122 and recovered as a PGM-enriched nickel alloy 132, e.g.,solidified in a mold to form ingots.

In any embodiment, the converter slag 130 can be smelted in the furnaces104 and/or 110. The slag 130 may contain residual PGM, and these valuescan be substantially recovered into the collector alloys 108 and/or 114.Preferably, at least a first portion 134 of the converter slag 130 isprocessed in the secondary furnace 110 with the primary furnace slag106, since this may aid in limiting the accumulation of deleteriouselements in the collector alloy 108 that can occur if the converter slag130 is processed only in the primary furnace 104.

In any embodiment, a second portion 136 of the converter slag 130 may berecycled to the converter feed 116.

With reference to FIG. 1C, embodiments of the present invention providea converter process 175 that partially pre-oxidizes collector alloy tospeed up the converting process. In the converter process 175, rawcollector alloy 108 and/or 114 (FIG. 1B) are contacted in step 180 withan oxidant 182 at elevated temperature to obtain a partiallypre-oxidized PGM collector alloy 184. The oxidant 182 can be anoxygen-containing gas such as air, oxygen-enriched air, oxygen,oxygen-rich combustion gas, or the like. The elevated temperature ispreferably not less than 800° C., and more preferably not less than2000° C.

In step 186, the partially pre-oxidized alloy 184 is often melted in thepot 120 of the converter 118 (FIG. 1A or 1B) using, for example, burnerassembly 117 (FIG. 1A), to form the alloy pool 122. In the convertingstep 187, converter feed 116 is introduced to the alloy pool 122 in thepot 120 and oxygen-containing gas 124 is injected. The converter feed116 preferably comprises the partially pre-oxidized alloy 184, the rawcollector alloy 108, 114, or a combination thereof. Then in step 188,the converter slag 130 can be tapped as needed, preferably a pluralityof times, and in step 189, the alloy pool 122 (FIG. 1A) is tapped, andPGM-enriched alloy 132 is recovered.

Pre-oxidation as shown in FIG. 1C solves problems in known convertingtechnology. For example, directly melting the PGM collector alloys 108,114 from the furnaces 104, 110, may produce an initial slag 128B (FIG.4) with undesirable melting characteristics. Also, the PGM collectoralloys may be undesirably reactive with oxygen, resulting in anexcessive exotherm, and/or requiring a relatively low rate of oxygenaddition and an extended period of time for suitable conversion.Preferably, the partial pre-oxidation in step 180 achieves from 10 to 90percent conversion of the iron to iron oxide in the collector alloy,more preferably from 25 to 75 percent iron conversion, and especiallyfrom 30 to 60 percent iron conversion. If desired, the oxidized iron canbe removed from the partially pre-oxidized PGM collector alloy 184,e.g., where prepared as a starter alloy in an earlier converter cyclefrom which slag is separated; or preferably the oxidized iron can remainin the partially pre-oxidized PGM collector alloy 184, as in airoxidation in a kiln or especially by flame oxidation.

With reference again to FIG. 1C, the process 175 can provide a converterstartup procedure. In any embodiment, a partially pre-oxidized collectoralloy charge is often used to speed up the converting process, e.g., theinitial melting, and/or produce an initial slag with a low meltingtemperature. In any embodiment, any metal that melts more quickly and/orat a lower temperature relative to the converter feed 116 (FIGS. 1A and1B) can be used as or in lieu of the partially pre-oxidized collectoralloy 184. In the converter startup procedure 175, raw collector alloy108 and/or 114 (FIG. 1B) are contacted in step 180 with anoxygen-containing gas 182 at elevated temperature to obtain a partiallypre-oxidized PGM collector alloy 184, which in turn is melted in step186 using, for example, burner assembly 117 (FIG. 1A), to form the alloypool 122 in the pot 120 of the converter 118 (FIG. 1A or 1B).

For example, the pre-oxidation 180 can be effected (1) by contactingparticles of the raw collector alloy 108/114 (e.g., crushing to a meshsize of −16 may be suitable, for example, −16 or −18/+200) with anoxygen-containing gas at a temperature of at least 800° C., for examplebetween 800° C. and 950° C., e.g., in a rotary kiln or fluidized bedroaster; (2) by partially converting the raw collector alloy inconverter 118 (FIG. 1A) with oxygen-containing gas 124 at a temperatureno less than 1250° C., preferably at least 1450° C., e.g., 1450° C. to1700° C., and tapping the partially oxidized alloy, e.g., in an earlieror previous converter cycle (see FIG. 1D); (3) by flame oxidationcomprising passing comminuted particles 157 (e.g., crushing to a meshsize of −16 may be suitable, for example, −16 or −18/+200) through anoxygen-rich flame 156 (FIG. 2C), preferably at a temperature not lessthan 2000° C., more preferably 2000° C. to 3500° C., and especially2000° C. to 2800° C.; and so on. Some preferred embodiments of flamepre-oxidation are described in more detail in reference to FIG. 2Cbelow.

With reference to FIG. 1D, there is schematically shown an example ofstarter alloy preparation procedure 190 to prepare partiallypre-oxidized starter alloy in an amount sufficient for a plurality ofbatches. In step 191, a charge of partially pre-oxidized collector alloy184 (FIG. 1C), e.g., from an earlier starter alloy batch, is placed inthe optionally emptied pot 120. In step 192, the starter alloy 186 ismelted, e.g., using burner assembly 117 (FIG. 1A) to form the converteralloy pool 122. In step 193, converter feed 116 comprising the PGMcollector alloy is supplied (periodically or continuously), and in step194, oxygen-containing gas 124 is injected into the alloy pool 122. Theoxygen injection is continued to partially oxidize the converter feed,preferably wherein from 10 to 90 percent of the iron is converted toiron oxide, more preferably where the iron conversion is from 25 to 75percent, and especially from 30 to 60 percent iron conversion, based onthe weight of iron in the total converter feed 116 and starter alloysupplied to the alloy pool 122. In step 195, the converter slag 130 canbe tapped as needed to avoid over-filling the pot 120, preferably aplurality of times.

Then in step 196, the alloy pool 122 (FIG. 1A) is tapped, and starteralloy 184′ is recovered. The recovered starter alloy 184′ is oftensolidified and broken up into pieces, or it can be comminuted, e.g., bycrushing, milling, etc., as desired, although this is not generally arequirement. For example, the solidified, partially oxidized collectoralloy from the starter alloy preparation cycle can be divided into aplurality of generally equal-sized starter alloy charges for a likeplurality of converter operating cycles and/or starter alloy preparationcycles. For example, one batch of starter alloy 184′ may providesufficient starter alloy for a plurality of batches, e.g., 3-10, andthus a starter batch prepared for seven batches might be prepared everyseventh batch, i.e., using the seventh one of the starter batches afterthe sixth batch of PGM-enriched nickel alloy product.

With reference to FIG. 2A, there is schematically shown a simplifiedside view of a preferred TBRC 118 equipped with a water-cooled oxy-fuelburner assembly 117, motor 119, fume hood 121, water cooled heat shield121A, oxygen injection lance 126, and rotary coupling 148. The TBRC 118has a fume hood 121 and a water cooled heat shield 121A that hasopenings to allow positioning of the burner 117 and lance 126, entry offeed 116 (FIG. 1A) and protectant 138 (FIG. 1A), and tapping of thealloy pool 122 (FIG. 1A) and low density layer 128 (FIG. 1A). The motor119 can be geared, e.g., via a chain 119A and sprockets 119B, 119C, andis capable of rotating the pot 120 at a suitable rate to provideagitation, e.g., ½ rotation per minute. Externally mounted transmitters144 can be connected via wire 141 through conduit 143 to temperaturesensors 140 (see FIG. 2B) mounted in or near the refractory 123 (seeFIG. 2B) can send a temperature signal to a remote receiver 145. Acooling fluid inlet and outlet can be in the form of flex hoses 147 aand 147 b to supply and return the cooling fluid via a dual flow rotarycoupling 148 to a jacket 146 (see FIG. 2B).

With reference to FIG. 2B there is shown a side sectional view of theTBRC 118 comprising the pot 120. A temperature sensor 140 such as athermocouple is located in the refractory 123, preferably adjacent aninterior wall 142 of the pot 120, and connected via wire 141 passingthrough conduit 143 to the externally mounted temperature transmitter144, which can transmit temperature information wirelessly to the remotereceiver 145 (FIG. 2A). In any embodiment, the oxygen-containing gas isinjected into the converter alloy pool at a sufficient rate to maintainthe alloy pool in a molten state at a temperature no higher than 1800°C., e.g., a temperature in the alloy pool not less than 1250° C.,preferably from about 1450° C. to 1700° C. Lower temperatures riskpremature solidification of the alloy pool 122, whereas excessively hightemperatures risk failure of TBRC 118 components. In any embodiment, thetemperature of the refractory 123 can be monitored, e.g., for processcontrol and/or to detect premature thinning.

In any embodiment, the pot 120 can be provided with a jacket 146 tocirculate coolant fluid such as an aqueous heat transfer medium, e.g.,water/ethylene glycol/propylene glycol, and the like. For example, thefluid from a flex hose 147 a can enter the jacket 146 through a centralpassage of a rotary coupling 148, flow into an inner annular channel 150adjacent the wall 142, and out through an outer annular channel 152 toexit via the coupling 148 from flex hose 147 b. In this manner, the lifeof the refractory 123 can be extended and/or the oxygen can be injectedat a higher rate to facilitate faster processing and/or a greaterconverter throughput. If desired, the bottom of the pot 120 and jacket146 can comprise a bottom flange (not shown) to facilitateassembly/disassembly.

With reference to FIG. 2C, there is shown a simplified side sectionalview of the TBRC 118 of FIGS. 2A and 2 B schematically illustrating anembodiment of a burner assembly 117 for in situ pre-oxidation accordingto embodiments of the present invention. The burner assembly 117 isprovided with a fuel/oxygen supply line(s) 154 to burner nozzle 155 togenerate an oxygen-rich flame 156. Collector alloy particles 157 aresupplied through an adjacent feeding tube 158, e.g., from an overheadvibrating feed unit (not shown). The collector alloy particles 157 fallfrom the feed tube 158 through the flame 156 where they are partiallyoxidized. The partially oxidized particles 157A then fall and accumulatein the pot 120. Rotation of the pot 120 during operation distributes theparticles 157A onto a surface of the refractory lining 123. If theparticles 157A are melted or partially melted in the flame 156, they canform a coating on the refractory lining 123 when they cool and solidify.Free-flowing and/or fused particles 157A can then be melted when desiredby increasing the firing rate of burner 156. If the burner 156 is firedat a higher rate during pre-oxidation, the partially oxidized particles157A can collect in a molten alloy pool 122A (see FIG. 3).

The collector alloy particles 157 are often ground or milled into aparticulated form to increase the surface area exposed to the flame 156,but are preferably sufficiently large to pass through the flame 156 andsettle on the pot 120. The alloy particles 157 are also preferablysufficiently large to facilitate separation, e.g., by cyclone (notshown) or gravity, and avoid excessive entrainment in the dischargedcombustion gas. For example, a mesh size of −16 or −18/+200 may besuitable for gravity separation. Excessive fines, e.g., −200 mesh, arepreferably minimized or avoided. The flame 156 is preferably oxygen-richto provide an oxidizing environment to partially oxidize the particles157, e.g., the burner 155 can be fired with a fuel gas such as naturalgas or propane and a 10% excess of oxygen relative to theoretical forcomplete combustion, preferably 15-30% excess oxygen, more preferably20-25% excess oxygen. The combustion oxidizing gas is preferablyoxygen-enriched air or more preferably >99 volume percent oxygen so thatthe combustion temperature in the flame 156 is no less than 2000° C. Thepartial pre-oxidation should be sufficient to convert from 10 to 90percent of the iron in the particles 157 to iron oxide in the particles157A, preferably to convert from 25 to 75 percent of the iron, and morepreferably to convert from 30 to 60 percent of the iron.

The collector alloy particles 157 can conveniently be pre-oxidizedduring an off shift, e.g., overnight, using a relatively low feed rateand a low burner rate, relative to operation. A charge of collectoralloy particles 157 sufficient to form the desired alloy pool 122A (FIG.3) at the start of an operating cycle can be loaded in the feed unit(not shown). The particles 157 can accumulate in a bed, a coating, or asa molten pool inside of the pot 120, which is kept hot by the flame 156.After the charge is finished pre-oxidizing, continued firing of theburner 155 facilitates keeping the pot 120 and partially pre-oxidizedcollector alloy particles 157 warm, e.g., 500° C. to 1200° C.,preferably 800° C. to 1200° C., so that a converting operating cycle canbe quickly started. At the start of the day shift, the accumulatedparticles 157 can be molten or quickly melted to form the alloy pool122A (see FIG. 3) by increasing the firing rate of the burner 155 toquickly start a converting cycle.

A preferred operational cycle of the converter 118 is shown in FIGS.3-7. An operating cycle often begins by melting a charge of partiallypre-oxidized collector alloy in the converter pot 120 to form theconverter alloy pool 122A as shown in FIG. 3. The pool 122A ispreferably just sufficient to inject the oxygen below the surface, e.g.,approximately 10-15 vol % of the available volume of the pot 120, wherethe available volume is the volume of the pot 120 that can be filledwithout overflowing material out of the top at the angle at which thepot 120 is inclined for operation. However, because the PGM collectoralloys 108, 114 from the furnaces 104, 110 may produce a slag (128B)with undesirable melting characteristics when melted, a partiallypre-oxidized collector alloy charge is preferably used to speed up theinitial melting and produce an initial slag with a low melting point. Inany embodiment, any metal that melts more quickly and/or at a lowertemperature relative to the converter feed 116 can be used as or in lieuof the partially pre-oxidized collector alloy.

After melting the initial pre-oxidized alloy charge 122A in FIG. 3, theconverter feed 116 is introduced and the oxygen is injected. The feedmaterial 116 is melted and the volume of the alloy pool 122B is enlargedas shown in FIG. 4. Reaction of the oxygen converts iron and othermaterials into a slag phase 128B, which reduces the alloy pool volume.The slag phase 128B is less dense than the alloy pool 122B, and floatson top. Agitation from oxygen-containing gas injection and/or rotationof the pot 120 entrains particles or droplets 160 of the alloy into theslag phase 128B.

Introduction of the feed 116 and oxygen-containing gas injection arecontinued until the pot 120 is filled to desired capacity with enlargedalloy pool 122C and slag phase 128C, as shown in FIG. 5. The slag phases128B and 128C during the pot fill stage generally contain some entrainedalloy 160 dispersed in the slag phases 128B, 128C due to agitation andmixing by the oxygen injection and rotation of the pot 120. The feedintroduction and oxygen injection are often stopped for slag tapping.When the oxygen injection and rotation are stopped, the entrained alloydroplets or particles 160 are allowed to settle out of the slag phase128D and return to the alloy pool 122D, as seen in FIG. 6. After aquiescence period effective to promote the gravity settling anddisentrainment of dispersed metal 160 from the slag 128C (FIG. 5), andcoalescence into the alloy pool 122D (FIG. 6), preferably at least 2minutes, the slag 128D can be removed with substantially less entrainedalloy. The slag 128D is often tapped by tilting the pot 120 to pour outthe slag phase 128D into molds (not shown), with minimal entrainment ortapping of the alloy pool 122D, i.e., with a clean margin for the slagphase 128D.

With the slag 128D removed, the pot 120 has additional volume to resumethe feed supply and/or oxygen injection as in FIGS. 3 and 4. The cycleof filling the pot as in FIGS. 4 and 5 and tapping the slag 128D, aftera brief alloy disentrainment period as shown in FIG. 6, is preferablyrepeated a plurality of times. After the desired charge of the converterfeed 116 has been added, the oxygen-containing gas injection maycontinue until the level of desired conversion is achieved, e.g., atleast 90% conversion of the iron from the converter feed 116, orpreferably at least 95% iron conversion, or more preferably 98% ironconversion. After a final cycle of filling and/or oxygen injection, thealloy pool 122E is at its desired volume and level of converting as inFIG. 7, and the final slag layer 128E and alloy pool 122E aresuccessively tapped and poured into respective molds.

When it is desired to tap the alloy 122E and final slag 128E as in FIG.7, however, it is preferred to immediately tap the slag 128E withoutwaiting for the alloy phase 160 to substantially separate from the slag128E. At the end of the oxygen injection, the converting reaction ismore complete and the exotherm may moderate, tending to reduce thetemperature of the alloy pool 122E. At the same time, the meltingtemperature of the PGM-enriched alloy has increased. Thus, it ispreferred to tap the alloy 122E promptly to avoid prematuresolidification, e.g., by commencing final tapping of the slag 128E lessthan 5 minutes following termination of the oxygen injection. To avoidcontaminating the alloy pool 122E with slag 128E, it is often preferredto tap the final slag 128E to provide the alloy pool 122E with a cleanmargin, i.e., by tapping an upper portion or surface at the upper marginof the alloy pool 122E with the slag 128E. However, as described above,this final slag tapping 128E represents a high grade slag that ispreferably recycled to the converter feed 116 in a subsequent convertercycle, so that the PGM values can be recovered.

In a preferred embodiment as shown schematically in FIG. 8, process 200includes smelting catalyst material 202 in primary electric arc furnace204. Slag 205, comprising mainly aluminosilicate, is recovered from thefurnace 204, granulated in water in granulator 206, dried in rotary kiln208, and repackaged in bag-filling station 210. The PGM collector alloy211 is cast into molds 212, solidified, and crushed in crusher 214.

The dried slag 210 from the primary furnace 204 is smelted in second,finishing electric arc furnace 218. Slag 219 recovered from the furnace218 is granulated in granulator 220 and recycled as byproduct 222 for anappropriate use, e.g., as aggregate. The PGM collector alloy 223 fromthe secondary furnace 218 is cast into molds 224, solidified and crushedin crusher 214.

Milled collector alloys 211 and 223 from crusher 214 are placed inhopper 225 which supplies feed material to vibrating feeder 226 to TBRC227. The TBRC 227 is equipped with a burner assembly 228, oxygeninjection lance 229, fume hood 230, and motor (see FIG. 2A) to rotatethe pot 232 of the TBRC 227. If desired, the pot 232 can be providedwith a water-cooling jacket, lined with an alumina-based rammingrefractory, and provided with any of the other features of the TBRC 118as described above in connection with FIGS. 2A, 2B, 2C.

To start a converting cycle, as the TBRC 227 is rotated, a portion ofthe converter feed from the hopper 225 is fed through the feeder 226 tofall through an oxygen-rich flame (cf. flame 156 in FIG. 2C) of theburner assembly 228 and is partially pre-oxidized. The pre-oxidation iscontinued until accumulating a charge of the partially pre-oxidizedcollector alloy that when melted would create an alloy pool ofsufficient size to allow oxidation to begin, generally filling about10-20% of the available volume of the pot. Cf. alloy pool 122A in FIG.3. Alternatively, a previously prepared starter alloy, a kiln-oxidizedcollector alloy, a fluidized bed oxidized collector alloy, or the likecould be used as the partially pre-oxidized collector alloy. Ifnecessary, the partially pre-oxidized collector alloy charge is meltedusing the burner 228 to a temperature of at least 1250° C., preferablyat least 1450° C. A portion of the total protectant comprising the driedaluminosilicate slag 210 from the primary furnace 204 is preferablyplaced on top of the alloy pool as slag protectant 233.

While the pot of the TBRC 227 is rotated, the burner is typically shutoff and oxygen 234 is injected into the alloy pool using lance 229 at arate to maintain a temperature sufficient to avoid solidification of thealloy pool but at a sufficient rate to maintain the temperature in thealloy pool no higher than 1800° C., e.g., 1450° C. to 1700° C. PGMcollector alloys 211, 223 from the furnaces 204, 218 are placed inhopper 225, and fed into the TBRC 227 at a generally steady rate viavibrating feeder 226. The TBRC 227 filled with material as slag isformed and the alloy pool grown by the feed into the TBRC. Cf alloy pool122B and slag 128B in FIG. 4. When the volume of the pot was filledsufficiently (cf. alloy pool 122C and slag 128C in FIG. 5), the potrotation, oxygen injection, and alloy feed can be stopped. After waitingseveral minutes, typically at least 5 minutes, to allow phase separation(cf. alloy pool 122D and slag 128D in FIG. 4), slag 242 is tapped intomolds 244 by tipping the TBRC 227, taking care to maintain a clearmargin in the slag 242 and avoid tapping excessive amounts of the alloy.

The oxygen injection and converter feed into the remaining alloy poolare then resumed until the TBRC 227 is again filled, and slag 242 tappedas described above. The cycle is repeated several times until the alloypool has grown to a desired volume for tapping. The last slag 242 tappedjust before tapping the alloy is preferably performed promptly afterstopping the oxygen injection and collector alloy feed to avoidfreezing, taking care that substantially all of the slag 242 is tapped,e.g., providing a clear margin for the alloy pool. Minor amounts ofalloy may optionally be entrained in the slag. Cf alloy pool 122E, slag128E, and alloy 160 in FIG. 7. However, the final slag tapping ispreferably recycled to the converter feed 116 in a subsequent cycle tominimize PGM losses. The PGM-enriched alloy 245 is then tapped intoingot molds 246, cooled, and solidified.

After the slag molds 244 are cooled, the solidified slag 248 is oftenfed through slag crusher 250 and magnetic separator 252. Thenon-magnetic fractions from the final slag tapping and the earliertappings can be sorted into containers 254 and 256, respectively. Thenon-magnetic fraction 256 can be smelted in the secondary furnace 218with the slag 210 from the primary furnace.

The magnetic fractions 258 from all of the converter slag and thenon-magnetic fraction 254 from the final slag tapping are preferablyplaced in the feed hopper 225 for a subsequent TBRC batch.Alternatively, the entirety of the final slag tapping can be placeddirectly in the hopper 225 with the collector alloy(s) 211, 223,bypassing the magnetic separator 252.

In another aspect, in reference to FIG. 9, embodiments of the presentinvention provide a PGM collector alloy converting process 300comprising: in step 302, introducing a converter feed 116 (FIG. 1A)comprising PGM collector alloy 108 and/or 114 (FIG. 1B) into a pot 120of a converter 118 (FIG. 1A) holding an alloy pool 122 (FIG. 1A); instep 304, injecting oxygen-containing gas 124 (FIG. 1A) into the alloypool; in step 306, recovering slag 130 (FIG. 1A) from the pot 120; instep 308, smelting the recovered slag 130 in a furnace 104 and/or 110(FIG. 1B), preferably a secondary furnace 110; in step 310, recoveringcollector alloy 108 and/or 114 (FIG. 1B) from the furnace 104 and/or110; optionally in step 312, introducing the collector alloy 108 and/or114 recovered from the furnace 104 and/or 110 in step 308 to theconverter feed 116 to the pot 120 with the alloy pool 122; and in step314, recovering PGM-enriched alloy 132 (FIG. 1A) from the pot 120. Theconverter feed 116 preferably comprises the collector alloys 108 and/or114 which comprise no less than 0.5 wt % PGM, no less than 40 wt % iron,and no less than 0.5 wt % nickel, based on the total weight of thecollector alloy. The converter feed 116 may optionally comprise an addedflux material, but if an added flux material comprises more than 10weight percent silica and more than 10 weight percent of calcium oxide,magnesium oxide, or a combination of calcium oxide and magnesium oxide,by weight of the added flux material, the converter feed preferablycomprises no more than 20 parts by weight of the added flux material per100 parts by weight of the collector alloy. Preferably, the PGM-enrichedalloy comprises no less than 25 wt % PGM, no less than 25 wt % nickel,and no more than 10 wt % iron, more preferably from 25 to 60 wt % PGMand from 25 to 70 wt % nickel.

In another aspect, in reference to FIG. 10, embodiments of the presentinvention provide a PGM collector alloy converting process 350comprising: in step 352, lining a converter pot 120 with a refractorymaterial 123 (FIG. 1A); in step 354, holding an alloy pool 122 (FIG. 1A)in the pot 120; in step 356, supplying a refractory protectant 138 (FIG.1A) to the pot 120 with the converter alloy pool 122; in step 358,introducing a converter feed 116 (FIG. 1A) comprising PGM collectoralloy 108 and/or 114 (FIG. 1B) into the pot 120 with the alloy pool 122;in step 360, injecting oxygen-containing gas 124 (FIG. 1A) into thealloy pool 122; in step 362, recovering slag 130 (FIG. 1A) from the pot120; and in step 364, recovering PGM-enriched alloy 132 from the pot120. The refractory protectant 138 preferably comprises a refractorycomponent in common with the refractory material 123. The component incommon can comprise alumina, for example. The converter feed 116preferably comprises the collector alloys 108 and/or 114 which compriseno less than 0.5 wt % PGM, no less than 40 wt % iron, and no less than0.5 wt % nickel, based on the total weight of the collector alloy. Theconverter feed 116 may optionally comprise an added flux material, butif an added flux material comprises more than 10 weight percent silicaand more than 10 weight percent of calcium oxide, magnesium oxide, or acombination of calcium oxide and magnesium oxide, by weight of the addedflux material, the converter feed preferably comprises no more than 20parts by weight of the added flux material per 100 parts by weight ofthe collector alloy. Preferably, the PGM-enriched alloy comprises noless than 25 wt % PGM, no less than 25 wt % nickel, and no more than 10wt % iron, more preferably from 25 to 60 wt % PGM and from 25 to 70 wt %nickel.

In another aspect, in reference to FIG. 11, embodiments of the presentinvention provide a PGM collector alloy converting process 400comprising: in step 402, placing a charge of partially pre-oxidized PGMcollector alloy 184 (see FIG. 1C) in a pot 120 of a converter 118 (FIG.1A); in step 404, melting the charge of the partially pre-oxidized PGMcollector alloy 184 to form an initial alloy pool 122A (FIG. 3), e.g.,using a burner assembly 117; in step 406, introducing a feed 116 (FIG.1A) comprising PGM collector alloy into the pot 120 with the alloy pool122A; in step 408, injecting oxygen-containing gas 124 (FIG. 1A) intothe alloy pool; in step 410, recovering slag 130 (FIG. 1A) from the pot120; and in step 412 recovering PGM-enriched alloy 132 from the pot 120.The converter feed 116 preferably comprises the collector alloys 108and/or 114 which comprise no less than 0.5 wt % PGM, no less than 40 wt% iron, and no less than 0.5 wt % nickel, based on the total weight ofthe collector alloy. The converter feed 116 may optionally comprise anadded flux material, but if an added flux material comprises more than10 weight percent silica and more than 10 weight percent of calciumoxide, magnesium oxide, or a combination of calcium oxide and magnesiumoxide, by weight of the added flux material, the converter feedpreferably comprises no more than 20 parts by weight of the added fluxmaterial per 100 parts by weight of the collector alloy. Preferably, thestarter charge forms an alloy pool comprising a volume of from 5 to 20vol % of available pot volume, or the depth is otherwise sufficient toreceive a lance for the oxygen-containing gas injection. Preferably, thePGM-enriched alloy comprises no less than 25 wt % PGM, no less than 25wt % nickel, and no more than 10 wt % iron, more preferably from 25 to60 wt % PGM and from 25 to 70 wt % nickel.

In yet another aspect, in reference to FIG. 12, embodiments of thepresent invention provide a PGM collector alloy converting process 450comprising: in step 452, holding an alloy pool 122 in a pot 120 (FIG.1A); in step 454, introducing a converter feed 116 (FIG. 1A) comprisingPGM collector alloy into the pot 120 with the alloy pool 122; in step456, injecting oxygen-containing gas 124 (FIG. 1A) into the alloy pool122; in step 458, recovering slag 130 from the pot 120; in step 460,separating the slag 130 into first and second portions 134, 136;optionally, in step 462, smelting the first portion 134 in a furnace 104and/or 110 (FIG. 1B); introducing the second portion 136 to theconverter feed 116 to the pot 120; and in step 464, recoveringPGM-enriched alloy 132 from the pot 120.

In any embodiment of the process 450, the converter feed 116 cancomprise a weight ratio of recycled slag 136 to collector alloy 108and/or 114 (see FIG. 1B) of from 1:20 to 1:2, preferably from 1:10 to3:10. Preferably, all or part of the second portion 136 of the recoveredslag has a higher PGM and/or nickel content relative to a PGM and/ornickel content of the first portion 134, and/or the second portion 136of the recovered slag has a nickel content greater than about 2 wt %.For example, the separation in step 460 can be according to magneticsusceptibility where the first portion 134 comprises thenon-magnetically susceptible fraction and the second portion 136comprises the magnetically susceptible fraction. As another example, thesecond portion 136 can comprise a slag 128D with entrained alloy 160 asshown and discussed in connection with FIG. 7. The converter feed 116preferably comprises the collector alloys 108 and/or 114 which compriseno less than 0.5 wt % PGM, no less than 40 wt % iron, and no less than0.5 wt % nickel, based on the total weight of the collector alloy. Theconverter feed 116 may optionally comprise an added flux material, butif an added flux material comprises more than 10 weight percent silicaand more than 10 weight percent of calcium oxide, magnesium oxide, or acombination of calcium oxide and magnesium oxide, by weight of the addedflux material, the converter feed preferably comprises no more than 20parts by weight of the added flux material per 100 parts by weight ofthe collector alloy.

In a further aspect, with reference to FIG. 13, embodiments of thepresent invention provide a PGM collector alloy converting process 500comprising: in step 502, holding an alloy pool 122 in a pot 120 (FIG.1A); in step 504, introducing a converter feed 116 comprising PGMcollector alloy 108 and/or 114 (see FIG. 1B) comprising iron and nickelinto the pot 120 with the alloy pool 122; in step 506, injectingoxygen-containing gas 124 (FIG. 1A) into the alloy pool 122; in step508, recovering slag 130 from the pot 120; in step 510, solidifying andcomminuting the recovered slag 130; in step 511, separating the slag 130into a high grade fraction for a recycling step 518 and a low gradefraction 524, where the high grade fraction has a higher PGM contentthan the low grade fraction 524; in step 518, introducing a recycleportion of the recovered slag comprising the magnetically susceptiblefraction 136 to the converter feed 116 for introduction into the pot120; and in step 520, recovering PGM-enriched alloy 132 from the pot120. In any embodiment, the separation step 511 can optionally comprisea magnetic separation step 512 to magnetically separate the comminutedslag into a non-magnetically susceptible fraction 134 and a magneticallysusceptible fraction 136 comprising high grade slag. In any embodiment,the recycle portion of the recovered slag in step 518 can optionallyinclude a first, high grade portion 522 of the non-magneticallysusceptible fraction 516. For example, the high grade portion 522 cancomprise slag 128E (FIG. 7) from a final tapping. A second, low gradepart 524 of the non-magnetically susceptible fraction 516 is notrecycled, and can be removed from the converting process, e.g., forsmelting in the secondary furnace 110. In any embodiment, the converterfeed 116 can comprise a weight ratio of slag 136 and 522 to collectoralloy of from 1:20 to 1:2, preferably from 1:10 to 3:10. Preferably, thetotal recycle portion 136 and 522 of the recovered slag 512 has a higherPGM content and/or nickel content relative to a non-recycled portion524. Often, the recycle portion of the recovered slag has a total nickelcontent not less than about 2 wt %.

In a further aspect, with reference to FIG. 14, embodiments of thepresent invention provide a converting process 550 for converting aconverter feed 116 comprising a collector alloy comprising no less than0.5 wt % PGM, no less than 40 wt % iron, and no less than 0.5 wt %nickel, based on the total weight of the collector alloy. The converterfeed 116 may optionally comprise an added flux material, but if an addedflux material comprises more than 10 weight percent silica and more than10 weight percent of calcium oxide, magnesium oxide, or a combination ofcalcium oxide and magnesium oxide, by weight of the added flux material,the converter feed preferably comprises no more than 20 parts by weightof the added flux material per 100 parts by weight of the collectoralloy.

The process 550 comprises: (a) in step 552, placing a charge of apartially pre-oxidized PGM collector alloy 184 (FIG. 1C) in a converterpot 120 (FIG. 1A); (b) in step 554, melting the charge of the partiallypre-oxidized PGM collector alloy 184 in the pot 120, e.g., using aburner assembly 117 (FIG. 1A), to form an alloy pool 122A (FIG. 3); (c)in step 556, periodically or continuously introducing a charge ofconverter feed 116 into the pot 120; (d) in step 558, injectingoxygen-containing gas 124 into the alloy pool to form slag 128B (FIG.4); (e) in preparation for one or more periodic non-final slag tappings,in step 560, allowing alloy 160 entrained in the slag 128C tosubstantially settle into the alloy pool 122D as seen in FIG. 5, e.g.,for a period of no less than 5 minutes; (f) then in step 562, tappingslag 128D from the pot 120; (g) repeating step 558 in (d) one or moretimes followed by steps 560 and 562 until a final time; (h) followingthe final step 558, in step 564, tapping the slag 128E with entrainedalloy 160 as seen in FIG. 7.

The converter feed introduction step 556 in (c) and theoxygen-containing gas injection step 558 in (d) are preferably stoppedfor the periodic slag tapping steps 562 in (e) and 564 in (h).Preferably, the oxygen-containing gas injection step 558 is continueduntil the alloy pool 122E comprises 10 wt % iron or less, morepreferably 5 wt % iron or less, by weight of the alloy pool. In anyembodiment, all or part of the converter slag 128E recovered from thefinal slag tapping in (h) can be introduced to the converter feed 116,e.g., in a later batch.

In a still further aspect, with reference to FIG. 1B, embodiments of thepresent invention provide a process 100B for recovering PGM fromcatalyst material, comprising: smelting a catalyst material 102 in aprimary furnace 104 to form slag 106 and a first collector alloy 108;recovering slag 106 from the primary furnace 104; smelting the primaryfurnace slag 106 in a secondary furnace 110 to form a second collectoralloy 114 in the secondary furnace 110; recovering slag 112 from thesecondary furnace 110; recovering the first and second collector alloys108, 114 from the respective first and secondary furnaces 104, 110;introducing converter feed 116 comprising the first and second collectoralloys 108, 114 into a pot 120 holding a converter alloy pool 122,wherein the first and second collector alloys 108, 114 preferablycomprise at least 0.5 wt % PGM, at least 40 wt % iron, and at least 0.5wt % nickel, based on the total weight of the converter feed 116;injecting oxygen-containing gas 124 into the converter alloy pool 122;recovering converter slag 130 from the pot 120; smelting at least afirst portion 134 of the converter slag 130 in the secondary furnace 110together with the primary furnace slag 106; and recovering PGM-enrichednickel alloy 132 from the pot 120. Optionally, a second portion 136 ofthe converter slag 130 is introduced to the converter feed 116 with thefirst and second PGM collector alloys 108, 114 to the pot 120.Preferably, the oxygen-containing gas injection is continued until theconverter alloy pool 122 comprises 10 wt % iron or less, more preferably5 wt % iron or less, by weight of the converter alloy pool.

Further still in another aspect, in reference to FIGS. 2A, 2B, and 2C,embodiments of the present invention provide a TBRC 118 comprising aninclinable pot 120; a burner assembly 117 for heating the pot 120; fluidinlet and outlet connections 147 a, 147 b to circulate cooling fluidthrough a jacket 146; a refractory lining 123 in the pot 120 for holdingan alloy pool 122 (FIG. 1A); a motor 119 to rotate the pot 120; and alance 126 for injecting oxygen into the alloy pool 122. Preferably, theTBRC 118 further comprises a plurality of temperature transmitters 144operably connected to a plurality of temperature sensors 140 positionedin radially spaced relationship in the refractory lining 123 adjacent aninterior wall 142 of the pot 120. Preferably, the TBRC 118 furthercomprises a feed channel 158 to supply particles to a flame 156 from aburner 155 of the burner assembly 117. In any embodiment, the TBRC 118may further comprise a fume hood 121 and/or a water-cooled heat shield121A.

Embodiments Listing

Accordingly, the present invention provides the following nonlimitingembodiments:

-   1. A process for converting platinum group metal (PGM) collector    alloy, comprising the steps of:

(a) introducing a converter feed into a pot of a converter holding amolten alloy pool, wherein the converter feed comprises:

-   -   (i) 100 parts by weight of a collector alloy comprising no less        than 0.5 wt % PGM, no less than 40 wt % iron, and no less than        0.5 wt % nickel, based on the total weight of the collector        alloy; and    -   (ii) if an added flux material comprises more than 10 weight        percent silica and more than 10 weight percent of calcium oxide,        magnesium oxide, or a combination of calcium oxide and magnesium        oxide, by weight of the added flux material, no more than 20        parts by weight of the added flux material;

(b) injecting oxygen-containing gas into the alloy pool to convert ironand one or more other oxidizable elements from the collector alloy tothe corresponding oxides and enrich PGM in the alloy pool;

(c) allowing a slag comprising the iron oxide to collect in alow-density layer above the alloy pool;

(d) tapping the low-density layer to recover the slag from theconverter; and

(e) tapping the alloy pool to recover the PGM-enriched alloy.

-   2. The process of embodiment 1, further comprising:

lining the pot with a refractory material; and

supplying a refractory protectant to the pot holding the alloy pool at arate up to 20 parts by weight refractory protectant per hundred parts byweight of the collector alloy in the converter feed, preferably not morethan 18 parts by weight per 100 parts by weight of the collector alloy,and more preferably at a rate between 5 and 15 parts by weightrefractory protectant per 100 parts by weight of the collector alloy.

-   3. The process of embodiment 2, wherein the refractory protectant is    supplied to the pot (i) after initially melting the alloy pool and    prior to commencing step (b), (ii) during one or both of steps (a)    and (b), and/or (iii) after stopping one or both of steps (a)    and (b) to tap the low-density layer in step (d), prior to resuming    said one or both of steps (a) and (b).-   4. The process of embodiment 2 or embodiment 3, wherein the    refractory protectant is supplied to the pot together with the    collector alloy introduced in step (a).-   5. The process of embodiment 2 or embodiment 3, wherein the    refractory protectant is supplied to the pot separately from the    collector alloy introduced in step (a), preferably wherein the    supply of refractory protectant to the pot is periodic.-   6. The process of any of embodiments 2 to 5, wherein the refractory    protectant comprises a component in common with the refractory    material, preferably wherein the component in common comprises    alumina.-   7. The process of any of embodiments 2 to 6, wherein the converter    feed comprises less than 20 parts by weight of any added flux    material, regardless of content of silica, calcium oxide, and/or    magnesium oxide, per 100 parts by weight collector alloy.-   8. The process of any of embodiments 2 to 7, further comprising    injecting the oxygen-containing gas into the alloy pool in step (b)    through a lance extended into the alloy pool, wherein the lance    comprises a consumable refractory material and is advanced into the    pool as a tip of the lance is consumed, wherein the consumable    refractory material comprises a component in common with the lining,    preferably wherein the component in common comprises alumina.-   9. The process of any of embodiments 2 to 8, wherein the refractory    material of the lining comprises a ramming refractory comprising    alumina, preferably wherein the ramming refractory comprises at    least 90 wt % alumina.-   10. The process of any of embodiments 2 to 9, further comprising:

sensing temperature in the refractory lining with radially spacedsensors mounted in the refractory lining;

communicating temperature sensing information from the sensors to one ormore transmitters; and

transmitting signals containing the temperature sensing information fromthe one or more transmitters to a receiver;

preferably wherein the sensors are mounted adjacent a metal wall of thepot and/or the one or more transmitters are mounted externally on thepot and wirelessly transmit the signals to the receiver.

-   11. The process of any of embodiments 2 to 10, further comprising    jacketing the pot and circulating a coolant, preferably water,    through the jacket during step (b).-   12. The process of any of embodiments 2 to 11, wherein the    oxygen-containing gas is injected into the converter alloy pool at a    sufficient rate to maintain the alloy pool in a molten state at a    temperature no higher than 1800° C., preferably at a temperature in    a range from about 1250° C. to 1700° C., more preferably 1450° C. to    1700° C.-   13. The process of any preceding embodiment, further comprising,    prior to step (a), the step of (I) partially pre-oxidizing a portion    of the collector alloy from a raw state, preferably wherein the    partial pre-oxidation in step (I) comprises from 10 to 90 percent    conversion of iron, more preferably from 25 to 75 percent iron    conversion, and even more preferably from 30 to 60 percent iron    conversion, based on the iron in the raw collector alloy portion    prior to step (I).-   14. The process of embodiment 13, wherein the pre-oxidizing in    step (I) comprises (I.A) passing particles of the raw collector    alloy through an oxygen-rich flame, preferably wherein the flame    exhibits a flame temperature of not less than 2000° C., more    preferably 2000° C. to 3500° C., and especially 2000° C. to 2800° C.-   15. The process of embodiment 14, wherein the oxygen rich flame is    produced by a burner for heating the pot, and further comprising    (I.B) depositing at least partially melted and/or pre-oxidized    collector alloy particles from the flame into the pot.-   16. The process of embodiment 14 or embodiment 15, further    comprising (I.C) cooling and solidifying the particles to form a    coating of the pre-oxidized collector alloy on an interior surface    of a refractory lining of the pot, wherein step (II) comprises    melting the coating.-   17. The process of any of embodiments 13 to 16, further comprising,    prior to step (a), the steps of:

(II) melting the partially pre-oxidized collector alloy in the pot toform a sufficient volume of the alloy pool for the injection of theoxygen-containing gas in step (b); and

(III) then commencing the converter feed introduction into the pot instep (a) and the oxygen-containing gas injection into the alloy pool instep (b).

-   18. The process of embodiment 17, wherein the pre-oxidizing in    step (I) comprises operating the converter through a cycle of steps    (II), (III), (a), (b), (c), (d), and (e) to prepare a partially    oxidized starter alloy, wherein the starter alloy preparation cycle    comprises:

melting a previously prepared charge of the partially oxidized starteralloy in the emptied pot to form the alloy pool;

periodically or continuously supplying the converter feed to the alloypool in step (a) concurrently with the injection of theoxygen-containing gas in step (b);

continuing the injection of the oxygen-containing gas to partiallyoxidize the alloy pool, preferably wherein from 10 to 90 percent, morepreferably from 25 to 75 percent, of iron in the converter feed isoxidized, based on the weight of iron in the converter feed supplied tothe converter alloy pool;

tapping the slag from the converter pot, preferably a plurality oftimes;

then recovering and solidifying the partially oxidized alloy pool; and

preferably dividing the solidified, partially oxidized collector alloyfrom the starter alloy preparation cycle into a plurality of starteralloy charges for a like plurality of converter operating cycles and/orstarter alloy preparation cycles.

-   19. The process of embodiment 13, wherein the pre-oxidizing in    step (I) comprises contacting particles of the collector alloy with    an oxygen-containing gas at a temperature of at least 800° C., for    example between 800° C. and 950° C., preferably in a rotary kiln or    fluidized bed roaster.-   20. The process of any preceding embodiment, further comprising the    steps of:

(A.1) separating the slag recovered in step (d) into a plurality ofportions;

(A.2) recycling a first one of the recovered slag portions from step(A.1) to the converter feed introduced to the pot in step (a), whereinthe converter feed comprises the recycled slag in an amount of fromabout 5 to 100 parts by weight per 100 parts by weight of the collectoralloy, preferably wherein the converter feed comprises the recycled slagin an amount of from 10 to 50 parts by weight per 100 parts by weight ofthe collector alloy.

-   21. The process of embodiment 20, further comprising (A.3) combining    the collector alloy and the recycle slag for concurrent introduction    in the converter feed in step (a), preferably from a single feed    unit.-   22. The process of embodiment 20 or embodiment 21, wherein the    recycled slag in step (A.2) comprises a high-grade portion of the    recovered slag from step (d) having a higher PGM content than an    average overall PGM content of the recovered slag from step (d)    and/or a nickel content greater than about 2 percent by weight of    the recycled slag.-   23. The process of any of embodiments 18 to 22, further comprising    the steps of:

(B.1) cooling, solidifying, and comminuting the recovered slag from step(d);

(B.2) magnetically separating the comminuted slag into a magneticallysusceptible fraction and a non-magnetically susceptible fraction;

(B.3) recycling the magnetically susceptible fraction to the converterfeed in step (A.2); and

(B.4) optionally recycling a portion of the non-magnetically susceptiblefraction to the converter feed in step (A.2).

-   24. The process of any of embodiments 20 to 23, further comprising    the steps of:

(C.1) prior to steps (a) to (e), beginning a converter operation cycleby melting a partially pre-oxidized collector alloy in the pot to formthe alloy pool;

(C.2) then, prior to step (e), repeating a sequence of steps (a), (b),(c), and (d) a plurality of times, wherein step (d) in each sequencefollows steps (b) and (c);

(C.3) recycling the slag recovered from a final tapping of thelow-density layer in step (d) in a last one of the sequences of step(C.2) to the converter feed in step (A.2) regardless of magneticsusceptibility, and/or recycling all or part of the non-magneticallysusceptible fraction separated in step (B.2) from the final tapping instep (d) to the converter feed in step (A.2); and

(C.4) after the final tapping of the low-density layer in step (d) inthe last one of the sequences of step (C.2), tapping the alloy pool instep (e).

-   25. The process of embodiment 24, further comprising the steps of:

(D.1) for the tapping(s) of the low-density layer preceding the finaltapping in step (C.2), allowing alloy entrained in the low-density layerto substantially settle into the alloy pool before the tapping of therespective low-density layer(s); and

(D.2) for the final tapping in step (C.2), quickly commencing thetapping to avoid freezing of the alloy pool, optionally resulting inentrainment of alloy in the low-density layer for the final tapping instep (C.2).

-   26. The process of any preceding embodiment, further comprising the    steps of:

(1) prior to steps (a) to (e), beginning a converter operation cycle bymelting a partially pre-oxidized collector alloy in the pot to form thealloy pool for step (a);

(2) then, prior to step (e), repeating a sequence of steps (a), (b),(c), and (d) a plurality of times, wherein step (d) in each sequencefollows steps (b) and (c);

(3) for the tapping(s) of the low-density layer in step (d) in eachsequence of step (2) preceding a final tapping of the low-density layerin step (d) in a final sequence of step (2), allowing alloy entrained inthe low-density layer to substantially settle into the alloy pool beforethe tapping of the respective low-density layer(s), preferably for aperiod of no less than 5 minutes following termination of theoxygen-containing gas injection in the respective step (b) of therespective sequence of step (2);

(4) for the final tapping of the low-density layer in the step (d) ofthe final sequence of step (2), conducting the final tapping promptly toavoid freezing of the alloy pool and optionally entraining alloy in thelow-density layer of the final tapping in step (d) of the final sequenceof step (2), preferably by starting the final tapping of the low-densitylayer in step (d) within a period of no more than 5 minutes followingtermination of the oxygen-containing gas injection in step (b) of thefinal sequence of step (2); and

(5) after the final tapping of the low-density layer in step (d) in thelast one of the sequences of step (2), tapping the alloy pool in step(e).

-   27. The process of embodiment 26, further comprising the steps of:

(6) cooling, solidifying, and comminuting the recovered slag from step(d) in each sequence of step (2); and

(7) recycling the slag recovered from the final tapping of thelow-density layer in step (d) in the final sequences of step (2) to theconverter feed in step (a).

-   28. The process of any preceding embodiment, further comprising the    steps of:

(E.1) smelting a catalyst material in a (preferably non-converting)primary furnace;

(E.2) recovering a primary furnace slag and a first collector alloy fromthe primary furnace;

(E.3) smelting the primary furnace slag in a (preferably non-converting)secondary furnace;

(E.4) recovering a secondary furnace slag and a second collector alloyfrom the secondary furnace;

(E.5) supplying the first and second collector alloys to converter feedin step (a); and

(E.6) supplying at least a portion of the slag recovered from theconverter in step (d) to the secondary furnace for smelting with theprimary furnace slag in step (E.3).

-   29. The process of embodiment 28, wherein the pot of the converter    is lined with a refractory material, and further comprising    supplying a portion of the primary furnace slag from step (E.2) to    the pot as a refractory protectant for steps (a) and (b), preferably    at a rate not more than 20 parts by weight of the primary furnace    slag per 100 parts by weight of the collector alloy, more preferably    18 parts by weight of the primary furnace slag per 100 parts by    weight of the collector alloy, more preferably at a rate between 5    and 15 parts by weight of the primary furnace slag per 100 parts by    weight of the collector alloy.-   30. The process of any preceding embodiment, wherein the    oxygen-containing gas injection in step (b) is continued until the    alloy pool comprises no more than about 10 wt % iron, preferably no    more than 5 wt % iron, by total weight of the alloy pool.-   31. The process of any preceding embodiment, wherein the collector    alloy comprises:

from 0.5 to 12 wt % PGM;

no less than 40 wt % iron, preferably 40 to 80 wt % iron;

no less than 0.5 wt % nickel, preferably 1 to 15 wt % nickel;

no more than 3 wt % sulfur, preferably no less than 0.1 wt % sulfur;

preferably no more than 3 wt % copper, more preferably 0.1 to 3 wt %copper; preferably no more than 2 wt % chromium, more preferably 0.1 to2 wt % chromium; and preferably no more than 20 wt % silicon, morepreferably 1 to 20 wt % silicon.

-   32. The process of any preceding embodiment, wherein the    PGM-enriched alloy comprises:

no less than 25 wt % PGM, preferably from 25 to 60 wt % PGM;

no less than 25 wt % nickel, preferably from 25 to 70 wt % nickel; and

preferably no more than 2 wt % silicon, no more than 2 wt % phosphorus,no more than 10 wt % copper, and no more than 2 wt % sulfur.

Low Flux Converter Process Embodiments

-   A1. A process for converting platinum group metal (PGM) collector    alloy, comprising the steps of:

(a) introducing a converter feed into a pot of a converter holding amolten alloy pool, wherein the converter feed comprises:

-   -   (i) 100 parts by weight of a collector alloy comprising no less        than 0.5 wt % PGM, no less than 40 wt % iron, and no less than        0.5 wt % nickel, based on the total weight of the collector        alloy; and    -   (ii) if an added flux material comprises more than 10 weight        percent silica and more than 10 weight percent of calcium oxide,        magnesium oxide, or a combination of calcium oxide and magnesium        oxide, by weight of the added flux material, no more than 20        parts by weight of the added flux material;

(b) injecting oxygen-containing gas into the alloy pool to convert ironfrom the collector alloy to iron oxide and enrich PGM in the alloy pool;

(c) allowing a slag comprising the iron oxide to collect in alow-density layer above the alloy pool;

(d) tapping the low-density layer to recover the slag from theconverter; and

(e) tapping the alloy pool to recover the PGM-enriched alloy.

-   A2. The process of embodiment A1, further comprising:

lining the pot with a refractory material; and

supplying a refractory protectant to the pot holding the alloy pool at arate up to 20 parts by weight refractory protectant per hundred parts byweight of the collector alloy in the converter feed, preferably not morethan 18 parts by weight per 100 parts by weight of the collector alloy,and more preferably at a rate between 5 and 15 parts by weightrefractory protectant per 100 parts by weight of the collector alloy.

-   A3. The process of embodiment A2, wherein the refractory protectant    is supplied to the pot (i) after initially melting the alloy pool    and prior to commencing step (b), (ii) during one or both of    steps (a) and (b), and/or (iii) after stopping one or both of    steps (a) and (b) to tap the low-density layer in step (d), prior to    resuming said one or both of steps (a) and (b).-   A4. The process of embodiment A3, wherein the refractory protectant    is supplied to the pot together with the collector alloy introduced    in step (a).-   A5. The process of embodiment A3, wherein the refractory protectant    is supplied to the pot separately from the collector alloy    introduced in step (a), preferably wherein the supply of refractory    protectant to the pot is periodic.-   A6. The process of any of embodiments A2 to A5, wherein the    refractory protectant comprises a component in common with the    refractory material, preferably wherein the component in common    comprises alumina.-   A7. The process of embodiment A6, further comprising injecting the    oxygen-containing gas into the alloy pool in step (b) through a    lance extended into the alloy pool, wherein the lance comprises a    consumable refractory material and is advanced into the pool as a    tip of the lance is consumed, wherein the consumable refractory    material comprises a component in common with the lining, preferably    wherein the component in common comprises alumina.-   A8. The process of any of embodiments A2 to A7, wherein the    refractory material of the lining comprises a ramming refractory    comprising alumina, preferably wherein the ramming refractory    comprises at least 90 wt % alumina.-   A9. The process of any of embodiments A2 to A8, further comprising:

sensing temperature in the refractory lining with radially spacedsensors mounted in the refractory lining;

communicating temperature sensing information from the sensors to one ormore transmitters; and

transmitting signals containing the temperature sensing information fromthe one or more transmitters to a receiver;

preferably wherein the sensors are mounted adjacent a metal wall of thepot and/or the one or more transmitters are mounted externally on thepot and wirelessly transmit the signals to the receiver.

-   A10. The process of any of embodiments A2 to A9, further comprising    jacketing the pot and circulating a coolant, preferably water and/or    an aqueous heat transfer medium, through the jacket during step (b).-   A11. The process of any of embodiments A2 to A10, wherein the    oxygen-containing gas is injected into the converter alloy pool at a    sufficient rate to maintain the alloy pool in a molten state at a    temperature no higher than 1800° C., preferably at a temperature in    a range from about 1250° C. to 1700° C., more preferably 1450° C. to    1700° C.-   A12. The process of any of embodiments A1 to A11, wherein the    oxygen-containing gas injection in step (b) is continued until the    alloy pool comprises no more than about 10 wt % iron, preferably no    more than 5 wt % iron, based on the total weight of the alloy pool.-   A13. The process of any of embodiments A1 to A12, wherein the    collector alloy comprises:

from 0.5 to 12 wt % PGM;

no less than 40 wt % iron, preferably 40 to 80 wt % iron;

no less than 0.5 wt % nickel, preferably 1 to 15 wt % nickel;

no more than 3 wt % sulfur, preferably no less than 0.1 wt % sulfur;

preferably no more than 3 wt % copper, more preferably 0.1 to 3 wt %copper; and preferably no more than 20 wt % silicon, more preferably 1to 20 wt % silicon.

-   A14. The process of embodiment A13, wherein the PGM-enriched alloy    comprises:-   no less than 25 wt % PGM, preferably from 25 to 60 wt % PGM;-   no less than 25 wt % nickel, preferably from 25 to 70 wt % nickel;    and-   preferably no more than 2 wt % silicon, no more than 2 wt %    phosphorus, no more than 10 wt % copper, and no more than 2 wt %    sulfur.-   A15. The process of any of embodiments A1 to A14, further comprising    partially pre-oxidizing at least a portion of the collector alloy    from a raw state, wherein of the 100 parts by weight of the    collector alloy introduced in the converter feed to the pot, the    converter feed comprises at least 20 parts by weight of the    partially pre-oxidized collector alloy, preferably, wherein the    partial pre-oxidizing comprises passing particles of the collector    alloy through an oxygen-rich flame, preferably wherein the flame    exhibits a flame temperature of not less than 2000° C., more    preferably 2000° C. to 3500° C., and especially 2000° C. to 2800° C.-   A16. The process of any of embodiments A1 to A15, wherein the    converter feed further comprises recycled converter slag in an    amount of from about 5 to 100 parts by weight per 100 parts by    weight of the collector alloy.-   A17. The process of any of embodiments A1 to A16, wherein the    converter has an operating cycle comprising the steps of:

(I) partially pre-oxidizing at least a portion of the collector alloy;

(II) melting a charge of the partially pre-oxidized collector alloy fromstep (I) in the pot of the converter to form an alloy pool to start theconverter operating cycle;

(III) introducing the converter feed into the pot with the alloy pool,wherein the converter feed comprises: (i) partially pre-oxidizedcollector alloy product from step (I), (ii) the collector alloy withoutpre-oxidation, or (iii) a combination thereof, wherein the converterfeed may optionally further comprise recycle slag from a previousconverter cycle;

(IV) injecting the oxygen-containing gas into the alloy pool for theconversion of the iron to iron oxide and the enrichment of the PGM inthe alloy pool;

(V) allowing the slag comprising the iron oxide to collect in thelow-density layer above the alloy pool;

(VI) terminating steps (III) and (IV) and tapping the low-density layerto recover the slag from the converter;

(VII) repeating a sequence of steps (III), (IV), (V), and (VI) aplurality of times, including one or more non-final sequences and afinal sequence, wherein step (VI) in each sequence follows steps (IV)and (V);

(VIII) prior to the tapping of the low-density layer in step (VI) ofeach non-final sequence, allowing alloy entrained in the low-densitylayer to substantially settle into the alloy pool following terminationof the oxygen-containing gas injection;

(IX) promptly commencing the tapping of the low-density layer followingtermination of the oxygen-containing gas injection in step (VI) in thefinal sequence wherein freezing of the alloy pool is avoided; and

(X) at an end of the converter cycle, tapping the alloy pool to recoverthe PGM-enriched alloy wherein freezing of the alloy pool is avoided.

-   A18. The process of any of embodiments A1 to A17, further comprising    the steps of:

(1) smelting a catalyst material in a (preferably non-converting)primary furnace;

(2) recovering a primary furnace slag and a first collector alloy fromthe primary furnace;

(3) smelting the primary furnace slag in a (preferably non-converting)secondary furnace, preferably with the addition of metallurgical coke;

(4) recovering a secondary furnace slag and a second collector alloyfrom the secondary furnace;

(5) wherein the converter feed comprises the first and second collectoralloys; and

(6) supplying at least a portion of the slag recovered from theconverter in step (d) to the secondary furnace for smelting with theprimary furnace slag in step (3).

-   A19. The process of any of embodiments A1 to A18, further    comprising:

(A) lining the pot with a refractory;

(B) holding the molten alloy pool in the refractory-lined pot;

(C) jacketing the pot; and

(D) circulating a coolant through the jacket.

-   A20. The process of any of embodiments A1 to A19, wherein the    converter comprises a rotary converter, wherein the rotary converter    comprises:

wherein the pot comprises an inclined pot mounted for rotation about alongitudinal axis;

a refractory lining in the pot for holding a molten alloy pool;

an opening in a top of the pot to introduce a converter feed into thepot with the alloy pool;

a lance for injecting oxygen-containing gas into the alloy pool;

a heat transfer jacket for the pot;

a coolant system to circulate a heat transfer medium through the jacket;and

a tap to recovery the slag and the alloy from the pot.

Partial Pre-Oxidation Converter Process Embodiments

-   B1. A process for converting platinum group metal (PGM) collector    alloy, comprising the steps of:

(I) partially pre-oxidizing at least a portion of a raw collector alloycomprising no less than 0.5 wt % PGM, no less than 40 wt % iron, and noless than 0.5 wt % nickel, based on the total weight of the collectoralloy;

(II) introducing a converter feed into a pot of a converter, wherein theconverter feed comprises:

-   -   (i) at least 20 parts by weight of the partially pre-oxidized        collector alloy product of step (I); and    -   (ii) up to 80 parts by weight of the raw collector alloy,        wherein the sum of the parts by weight of the raw collector        alloy and the partially pre-oxidized collector alloy product of        step (I) equals 100;

(III) melting the converter feed to form an alloy pool in the pot;

(IV) injecting oxygen-containing gas into the alloy pool to convert ironto iron oxide and enrich PGM in the alloy pool;

(V) allowing a slag comprising the iron oxide to collect in alow-density layer above the alloy pool;

(VI) tapping the low-density layer to recover the slag from theconverter; and

(VII) tapping the alloy pool to recover the PGM-enriched alloy.

-   B2. The process of embodiment B1, wherein the partial pre-oxidation    in step (I)-   comprises from 10 to 90 percent conversion of iron, more preferably    from 25 to 75 percent iron conversion, and even more preferably from    30 to 60 percent iron conversion, based on the iron in the raw    collector alloy prior to step (I).-   B3. The process of embodiment B1 or embodiment B2, wherein the    pre-oxidizing in step (I) comprises (I.A) passing particles of the    raw collector alloy through an oxygen-rich flame, preferably wherein    the flame exhibits a flame temperature of not less than 2000° C.,    more preferably 2000° C. to 3500° C., and especially 2000° C. to    2800° C.-   B4. The process of embodiment B3, wherein the oxygen rich flame is    produced by a burner for heating the pot, and further comprising    (I.B) depositing at least partially melted pre-oxidized collector    alloy particles from the flame into the pot.-   B5. The process of embodiment B4, further comprising the steps of:

(I.C) cooling and solidifying the particles to form a coating of thepre-oxidized collector alloy on an interior surface of a refractorylining of the pot;

wherein step (III) comprises melting the coating in the pot to form asufficient volume of the alloy pool for the injection of theoxygen-containing gas in step (IV); and

wherein step (II) comprises introducing the converter feed into thealloy pool.

-   B6. The process of any of embodiments B1 to B5, further comprising:

wherein step (III) comprises melting the partially pre-oxidizedcollector alloy in the pot to form a sufficient volume of the alloy poolfor the injection of the oxygen-containing gas in step (IV); and

wherein step (II) comprises introducing the converter feed into thealloy pool.

-   B7. The process of embodiment B6, wherein the pre-oxidizing in    step (I) comprises operating the converter through a cycle of steps    (III), (II), (IV), (V), (VI), and (VII) to prepare a partially    oxidized starter alloy, wherein the starter alloy preparation cycle    comprises:

melting a previously prepared charge of the partially oxidized starteralloy in the emptied pot to form the alloy pool;

periodically or continuously supplying the converter feed to the alloypool in step (II) concurrently with the injection of theoxygen-containing gas in step (IV);

continuing the injection of the oxygen-containing gas to partiallyoxidize the alloy pool, preferably wherein from 10 to 90 percent, morepreferably from 25 to 75 percent, of iron in the converter feed isoxidized, based on the weight of iron in the converter feed supplied tothe converter alloy pool;

tapping the slag from the converter pot, preferably a plurality oftimes;

then recovering and solidifying the partially oxidized alloy pool; and

preferably dividing the solidified, partially oxidized collector alloyfrom the starter alloy preparation cycle into a plurality of starteralloy charges for a like plurality of converter operating cycles and/orstarter alloy preparation cycles.

-   B8. The process of any of embodiments B1 to B7, wherein the    pre-oxidizing in step (I) comprises contacting particles of the raw    collector alloy with an oxygen-containing gas at a temperature above    800° C., preferably between 800° C. and 950° C., preferably in a    rotary kiln or fluidized bed roaster.-   B9. The process of any of embodiments B1 to B8, wherein the    oxygen-containing gas injection in step (IV) is continued until the    alloy pool comprises no more than about 10 wt % iron, preferably no    more than 5 wt % iron, based on the total weight of the alloy pool.-   B10. The process of any of embodiments B1 to B9, wherein the raw    collector alloy comprises:

from 0.5 to 12 wt % PGM;

no less than 40 wt % iron, preferably 40 to 80 wt % iron;

no less than 0.5 wt % nickel, preferably 1 to 15 wt % nickel;

no more than 3 wt % sulfur, preferably no less than 0.1 wt % sulfur;

preferably no more than 3 wt % copper, more preferably 0.1 to 3 wt %copper; and preferably no more than 20 wt % silicon, more preferably 1to 20 wt % silicon.

-   B11. The process of embodiment B10, wherein the PGM-enriched alloy    comprises:

no less than 25 wt % PGM, preferably from 25 to 60 wt % PGM;

no less than 25 wt % nickel, preferably from 25 to 70 wt % nickel; and

preferably no more than 2 wt % silicon, no more than 2 wt % phosphorus,no more than 10 wt % copper, and no more than 2 wt % sulfur.

-   B12. The process of any of embodiments B1 to B11, wherein the    converter feed comprises:

(i) 100 parts by weight total of the raw collector alloy and thepartially pre-oxidized collector alloy; and

(ii) no more than 20 parts by weight of an added flux materialcomprising more than 10 weight percent silica and more than 10 weightpercent of calcium oxide, magnesium oxide, or a combination of calciumoxide and magnesium oxide, by weight of the added flux material.

-   B13. The process of embodiment B12, further comprising:

lining the pot with a refractory material; and

supplying a refractory protectant to the pot holding the alloy pool at arate up to 20 parts by weight refractory protectant per hundred parts byweight of the raw collector alloy and partially pre-oxidized collectoralloy in the converter feed, preferably not more than 18 parts by weightper 100 parts by weight of the raw collector alloy and partiallypre-oxidized collector alloy, and more preferably at a rate between 5and 15 parts by weight refractory protectant per 100 parts by weight ofthe raw collector alloy and partially pre-oxidized collector alloy.

-   B14. The process of embodiment B13, wherein the refractory    protectant comprises a component in common with the refractory    material, preferably wherein the component in common comprises    alumina.-   B15. The process of any of embodiments B1 to B15, wherein the    converter feed further comprises recycled converter slag in an    amount of from about 5 to 100 parts by weight per 100 parts by    weight total of the raw collector alloy and the partially    pre-oxidized collector alloy product of step (I) in the converter    feed.-   B16. The process of any of embodiments B1 to B15, wherein the    converter has an operating cycle comprising the steps of:

(1) melting a charge of the partially pre-oxidized collector alloy fromstep (I) in the pot of the converter to form the alloy pool to start theconverter operating cycle;

(2) the introduction of the converter feed into the pot with the alloypool in step (II), wherein the converter feed may optionally furthercomprise recycle slag from a previous converter cycle;

(3) the injecting of the oxygen-containing gas into the alloy pool forthe conversion of the iron to iron oxide and the enrichment of the PGMin the alloy pool in step (IV);

(4) the allowing of the slag comprising the iron oxide to collect in thelow-density layer above the alloy pool in step (V);

(5) terminating steps (2) and (3) and tapping the low-density layer torecover the slag from the converter;

(6) repeating a sequence of steps (2), (3), (4), and (5) a plurality oftimes, including one or more non-final sequences and a final sequence,wherein step (5) in each sequence follows steps (3) and (4);

(7) prior to the tapping of the low-density layer in step (6) of eachnon-final sequence, allowing alloy entrained in the low-density layer tosubstantially settle into the alloy pool following termination of theoxygen-containing gas injection;

(8) promptly commencing the tapping of the low-density layer followingtermination of the oxygen-containing gas injection in step (6) in thefinal sequence wherein freezing of the alloy pool is avoided and whereinalloy is optionally entrained in the low-density layer; and

(9) at an end of the converter cycle, tapping the alloy pool to recoverthe PGM-enriched alloy wherein freezing of the alloy pool is avoided.

-   B17. The process of any of embodiments B1 to B16, further comprising    the steps of:

(1) smelting a catalyst material in a (preferably non-converting)primary furnace;

(2) recovering a primary furnace slag and a first collector alloy fromthe primary furnace;

(3) smelting the primary furnace slag in a (preferably non-converting)secondary furnace, preferably with the addition of metallurgical coke;

(4) recovering a secondary furnace slag and a second collector alloyfrom the secondary furnace;

(5) wherein the first and/or second collector alloys are partiallypre-oxidized in step (I), and wherein the converter feed in step (II)comprises the first and/or second collector alloys and/or the partiallypre-oxidized collector alloy from step (I); and

(6) supplying at least a portion of the slag recovered from theconverter in step (d) to the secondary furnace for smelting with theprimary furnace slag in step (3).

-   B18. The process of any of embodiments B1 to B17, further    comprising:

(A) lining the pot with a refractory;

(B) holding the molten alloy pool in the refractory-lined pot;

(C) jacketing the pot; and

(D) circulating a coolant through the jacket.

-   B19. The process of any of embodiments B1 to B18, wherein the    converter comprises a rotary converter, wherein the rotary converter    comprises:

wherein the pot comprises an inclined pot mounted for rotation about alongitudinal axis;

a refractory lining in the pot for holding a molten alloy pool;

an opening in a top of the pot to introduce a converter feed into thepot with the alloy pool;

a lance for injecting oxygen-containing gas into the alloy pool;

a heat transfer jacket for the pot;

a coolant system to circulate a heat transfer medium through the jacket;and

a tap to recovery the slag and the alloy from the pot.

Converter Process with Slag Recycle

-   C1. A process for converting platinum group metal (PGM) collector    alloy, comprising a cycle of the steps of:

(a) introducing a converter feed into a pot of a converter holding amolten alloy pool, wherein the converter feed comprises:

-   -   (i) 100 parts by weight of a collector alloy comprising no less        than 0.5 wt % PGM, no less than 40 wt % iron, and no less than        0.5 wt % nickel, based on the total weight of the collector        alloy; and    -   (ii) recycled converter slag in an amount of from about 5 to 100        parts by weight per 100 parts by weight of the collector alloy;

(b) injecting oxygen-containing gas into the alloy pool to convert ironfrom the collector alloy to iron oxide and enrich PGM in the alloy pool;

(c) allowing a slag comprising the iron oxide to collect in alow-density layer above the alloy pool;

(d) tapping the low-density layer to recover the slag from theconverter;

(e) separating the slag recovered in step (d) into a slag portion forrecycle to converter feed in step (a) and a slag portion for production;and

(f) tapping the alloy pool to recover the PGM-enriched alloy.

-   C2. The process of embodiment C1, wherein the recycle slag portion    from step (e) of one cycle is supplied as the recycled converter    slag in step (a) in a subsequent cycle.-   C3. The process of embodiment C1 or embodiment C2, wherein the    converter feed comprises the recycled slag in an amount of from 10    to 50 parts by weight per 100 parts by weight of the collector    alloy.-   C4. The process of any of embodiments C1 to C3, further comprising    combining the collector alloy and the recycle slag for concurrent    introduction in the converter feed in step (a), preferably from a    single feed unit.-   C5. The process of any of embodiments C1 to C4, wherein the recycled    slag in step (a) and/or the recycle slag portion in step (e)    comprise high-grade slag having a higher PGM content than an average    overall PGM content of the recovered slag from step (d).-   C6. The process of embodiment C5, further comprising:

cooling, solidifying, and comminuting the recovered slag from step (d);

wherein the separation in step (e) comprises magnetically separating thecomminuted slag into a magnetically susceptible fraction and anon-magnetically susceptible fraction;

wherein the recycle slag portion comprises the magnetically susceptiblefraction; and

wherein the recycle slag portion optionally comprises a portion of thenon-magnetically susceptible fraction.

-   C7. The process of embodiment C6, further comprising the steps of:

(C.1) prior to steps (a) to (e), beginning a converter operation cycleby melting a partially pre-oxidized collector alloy in the pot to formthe alloy pool;

(C.2) then, prior to step (e), repeating a sequence of steps (a), (b),(c), and (d) a plurality of times, wherein step (d) in each sequencefollows steps (b) and (c);

wherein recycle slag portion from step (e) comprises the slag recoveredfrom a final tapping of the low-density layer in step (d) in a last oneof the sequences of step (C.2) regardless of magnetic susceptibility;and

(C.3) after the final tapping of the low-density layer in step (d) inthe last one of the sequences of step (C.2), tapping the alloy pool instep (e).

-   C8. The process of embodiment C6, further comprising the steps of:

(C.1) prior to steps (a) to (e), beginning a converter operation cycleby melting a partially pre-oxidized collector alloy in the pot to formthe alloy pool;

(C.2) then, prior to step (e), repeating a sequence of steps (a), (b),(c), and (d) a plurality of times, wherein step (d) in each sequencefollows steps (b) and (c);

wherein recycle slag portion from step (e) comprises all or part of thenon-magnetically susceptible fraction of the slag recovered from a finaltapping of the low-density layer in step (d) in a last one of thesequences of step (C.2); and

(C.3) after the final tapping of the low-density layer in step (d) inthe last one of the sequences of step (C.2), tapping the alloy pool instep (e).

-   C9. The process of embodiment C8, further comprising the steps of:

(D.1) for the tapping(s) of the low-density layer preceding the finaltapping in step (C.2), allowing alloy entrained in the low-density layerto substantially settle into the alloy pool before the tapping of therespective low-density layer(s); and

(D.2) commencing the final tapping in step (C.2) within 5 minutes ofstopping oxygen-containing gas injection.

-   C10. The process of any of embodiments C5 to C9, wherein the high    grade slag comprises more than 1000 ppm PGM and the production slag    portion comprises less than 1000 ppm PGM.-   C11. The process of any of embodiments C1 to C10, wherein the    oxygen-containing gas injection in step (b) is continued until the    alloy pool comprises no more than about 10 wt % iron, preferably no    more than 5 wt % iron, based on the total weight of the alloy pool.-   C12. The process of any of embodiments C1 to C11, wherein the    collector alloy comprises:

from 0.5 to 12 wt % PGM;

no less than 40 wt % iron, preferably 40 to 80 wt % iron;

no less than 0.5 wt % nickel, preferably 1 to 15 wt % nickel;

no more than 3 wt % sulfur, preferably no less than 0.1 wt % sulfur;

preferably no more than 3 wt % copper, more preferably 0.1 to 3 wt %copper; and preferably no more than 20 wt % silicon, more preferably 1to 20 wt % silicon.

-   C13. The process of embodiment C12, wherein the PGM-enriched alloy    comprises:

no less than 25 wt % PGM, preferably from 25 to 60 wt % PGM;

no less than 25 wt % nickel, preferably from 25 to 70 wt % nickel; and

preferably no more than 2 wt % silicon, no more than 2 wt % phosphorus,no more than 10 wt % copper, and no more than 2 wt % sulfur.

-   C14. The process of any of embodiments C1 to C13, wherein the    converter feed comprises:

(i) 100 parts by weight of the collector alloy; and

(ii) no more than 20 parts by weight of an added flux materialcomprising more than 10 weight percent silica and more than 10 weightpercent of calcium oxide, magnesium oxide, or a combination of calciumoxide and magnesium oxide, by weight of the added flux material.

-   C15. The process of any of embodiments C1 to C14, further    comprising:

lining the pot with a refractory material; and

supplying a refractory protectant to the pot holding the alloy pool at arate up to 20 parts by weight refractory protectant per hundred parts byweight of the collector alloy in the converter feed, preferably not morethan 18 parts by weight per 100 parts by weight of the collector alloy,and more preferably at a rate between 5 and 15 parts by weightrefractory protectant per 100 parts by weight of the collector alloy,preferably wherein the refractory protectant comprises a component incommon with the refractory material, preferably wherein the component incommon comprises alumina.

-   C16. The process of any of embodiments C1 to C15, further comprising    partially pre-oxidizing at least a portion of the collector alloy    from a raw state, wherein of the 100 parts by weight of the    collector alloy introduced in the converter feed to the pot, the    converter feed comprises at least 20 parts by weight of the    partially pre-oxidized collector alloy, preferably, wherein the    partial pre-oxidizing comprises passing particles of the raw    collector alloy through an oxygen-rich flame, preferably wherein the    flame exhibits a flame temperature of not less than 2000° C., more    preferably 2000° C. to 3500° C., and especially 2000° C. to 2800° C.-   C17. The process of any of embodiments C1 to C16, wherein the    converter has an operating cycle comprising the steps of:

(1) melting a charge of a partially pre-oxidized collector alloy in thepot of the converter to form the alloy pool to start the converteroperating cycle;

(2) the introduction of the converter feed into the pot with the alloypool in step (a), wherein the converter feed may optionally furthercomprise recycle slag from a previous converter cycle;

(3) the injecting of the oxygen-containing gas into the alloy pool forthe conversion of the iron to iron oxide and the enrichment of the PGMin the alloy pool in step (b);

(4) the allowing of the slag comprising the iron oxide to collect in thelow-density layer above the alloy pool in step (c);

(5) terminating steps (2) and (3) and tapping the low-density layer torecover the slag from the converter;

(6) repeating a sequence of steps (2), (3), (4), and (5) a plurality oftimes, including one or more non-final sequences and a final sequence,wherein step (5) in each sequence follows steps (2) and (3);

(7) prior to the tapping of the low-density layer in step (6) of eachnon-final sequence, allowing alloy entrained in the low-density layer tosubstantially settle into the alloy pool following termination of theoxygen-containing gas injection;

(8) promptly commencing the tapping of the low-density layer followingtermination of the oxygen-containing gas injection in step (6) in thefinal sequence wherein freezing of the alloy pool is avoided and whereinalloy is optionally entrained in the low-density layer; and

(9) at an end of the converter cycle, tapping the alloy pool to recoverthe PGM-enriched alloy wherein freezing of the alloy pool is avoided.

-   C18. The process of any of embodiments C1 to C17, further comprising    the steps of:

(1) smelting a catalyst material in a (preferably non-converting)primary furnace;

(2) recovering a primary furnace slag and a first collector alloy fromthe primary furnace;

(3) smelting the primary furnace slag in a (preferably non-converting)secondary furnace, preferably with the addition of metallurgical coke;

(4) recovering a secondary furnace slag and a second collector alloyfrom the secondary furnace;

(5) wherein the first and/or second collector alloys are partiallypre-oxidized in step (I), and wherein the converter feed in step (II)comprises the first and/or second collector alloys and/or the partiallypre-oxidized collector alloy from step (I); and

(6) supplying at least a portion of the slag recovered from theconverter in step (d) to the secondary furnace for smelting with theprimary furnace slag in step (3).

-   C19. The process of any of embodiments C1 to C18, further    comprising:

(A) lining the pot with a refractory;

(B) holding the molten alloy pool in the refractory-lined pot;

(C) jacketing the pot; and

(D) circulating a coolant through the jacket.

-   C20 The process of any of embodiments C1 to C19, wherein the    converter comprises a rotary converter, wherein the rotary converter    comprises:

wherein the pot comprises an inclined pot mounted for rotation about alongitudinal axis;

a refractory lining in the pot for holding a molten alloy pool;

an opening in a top of the pot to introduce a converter feed into thepot with the alloy pool;

a lance for injecting oxygen-containing gas into the alloy pool;

a heat transfer jacket for the pot;

a coolant system to circulate a heat transfer medium through the jacket;and

a tap to recovery the slag and the alloy from the pot.

Converter Process with Staged Slag Tapping

-   D1. A process for converting platinum group metal (PGM) collector    alloy, comprising the steps of:

(I) partially pre-oxidizing at least a portion of a raw collector alloycomprising no less than 0.5 wt % PGM, no less than 40 wt % iron, and noless than 0.5 wt % nickel, based on the total weight of the rawcollector alloy;

(II) melting a charge of the partially pre-oxidized collector alloy fromstep (I) in a pot of a converter to form an alloy pool to start aconverter cycle;

(III) introducing a converter feed into the pot with the alloy pool,wherein the converter feed comprises: (i) partially pre-oxidizedcollector alloy product from step (I), (ii) the raw collector alloy, or(iii) a combination thereof, wherein the converter feed may optionallyfurther comprise recycle slag from a previous converter cycle;

(IV) injecting oxygen-containing gas into the alloy pool to convert ironto iron oxide and enrich PGM in the alloy pool;

(V) allowing a slag comprising the iron oxide to collect in alow-density layer above the alloy pool;

(VI) terminating steps (III) and (IV) and tapping the low-density layerto recover the slag from the converter;

(VII) repeating a sequence of steps (III), (IV), (V), and (VI) aplurality of times, including one or more non-final sequences and afinal sequence, wherein step (VI) in each sequence follows steps (IV)and (V);

(VIII) prior to the tapping of the low-density layer in step (VI) ofeach non-final sequence, allowing alloy entrained in the low-densitylayer to substantially settle into the alloy pool following terminationof the oxygen-containing gas injection;

(IX) promptly commencing the tapping of the low-density layer followingtermination of the oxygen-containing gas injection in step (VI) in thefinal sequence wherein freezing of the alloy pool is avoided; and

(X) at an end of the converter cycle, tapping the alloy pool to recoverthe PGM-enriched alloy wherein freezing of the alloy pool is avoided.

-   D2. The process of embodiment D1, wherein an elapsed time between    termination of the oxygen-containing gas injection and commencement    of the low-density layer tapping in step (VIII) is no less than 5    minutes.-   D3. The process of embodiment D1 or embodiment D2, wherein an    elapsed time between termination of the oxygen-containing gas    injection and commencement of the low-density layer tapping in    step (IX) is no more than 5 minutes.-   D4. The process of any of embodiments D1 to D3, further comprising    entraining alloy in the low-density layer tapped in step (IX).-   D5. The process of any of embodiments D1 to D4, further comprising    the steps of:

(XI) cooling, solidifying, and comminuting the recovered slag from step(VI); and

(XII) separating the recovered slag from step (VI) into a slag portionfor recycle to converter feed in step (III) of a subsequent convertercycle, and a slag portion for production.

-   D6. The process of embodiment D5, wherein the converter feed in    step (III) comprises the recycled slag in an amount of from 10 to 50    parts by weight per 100 parts by weight of the collector alloy.-   D7. The process of embodiment D5 or embodiment D6, wherein the    recycle slag in step (III) and/or the recycle slag portion in    step (XII) comprise high-grade slag having a higher PGM content than    an average overall PGM content of the recovered slag from step (VI),    preferably wherein the high-grade slag comprises more than 1000 ppm    PGM and the production slag portion comprises less than 1000 ppm    PGM.-   D8. The process of any of embodiments D5 to D7, further comprising:

wherein the separation in step (XII) comprises magnetically separatingthe comminuted slag into a magnetically susceptible fraction and anon-magnetically susceptible fraction;

wherein the recycle slag portion comprises the magnetically susceptiblefraction; and

wherein the recycle slag portion optionally further comprises a portionof the non-magnetically susceptible fraction.

-   D9. The process of embodiment D8, wherein the recycle slag portion    further comprises the non-magnetically susceptible fraction from the    slag recovered from step (IX) in the final sequence.-   D10. The process of any of embodiments D5 to D9, wherein the recycle    slag portion comprises the slag recovered from step (IX) in the    final sequence regardless of magnetic susceptibility.-   D11. The process of any of embodiments D1 to D10, wherein the    oxygen-containing gas injection in step (IV) is continued until the    alloy pool comprises no more than about 10 wt % iron, preferably no    more than 5 wt % iron, based on the total weight of the alloy pool.-   D12. The process of any of embodiments D1 to D11, wherein the    collector alloy comprises:

from 0.5 to 12 wt % PGM;

no less than 40 wt % iron, preferably 40 to 80 wt % iron;

no less than 0.5 wt % nickel, preferably 1 to 15 wt % nickel;

no more than 3 wt % sulfur, preferably no less than 0.1 wt % sulfur;

preferably no more than 3 wt % copper, more preferably 0.1 to 3 wt %copper; and preferably no more than 20 wt % silicon, more preferably 1to 20 wt % silicon.

-   D13. The process of embodiment D12, wherein the PGM-enriched alloy    comprises:

no less than 25 wt % PGM, preferably from 25 to 60 wt % PGM;

no less than 25 wt % nickel, preferably from 25 to 70 wt % nickel; and

preferably no more than 2 wt % silicon, no more than 2 wt % phosphorus,no more than 10 wt % copper, and no more than 2 wt % sulfur.

-   D14. The process of any of embodiments D1 to D13, wherein the    converter feed comprises:

(i) 100 parts by weight total of the raw collector alloy and partiallypre-oxidized collector alloy; and

(ii) no more than 20 parts by weight of an added flux materialcomprising more than 10 weight percent silica and more than 10 weightpercent of calcium oxide, magnesium oxide, or a combination of calciumoxide and magnesium oxide, by weight of the added flux material.

-   D15. The process of any of embodiments D1 to D14, further    comprising:

lining the pot with a refractory material; and

supplying a refractory protectant to the pot holding the alloy pool at arate up to 20 parts by weight refractory protectant per hundred parts byweight total of the raw collector alloy and partially pre-oxidizedcollector alloy in the converter feed, preferably not more than 18 partsby weight per 100 parts by weight total of the raw collector alloy andpartially pre-oxidized collector alloy, and more preferably at a ratebetween 5 and 15 parts by weight refractory protectant per 100 parts byweight total of the raw collector alloy and partially pre-oxidizedcollector alloy, preferably wherein the refractory protectant comprisesa component in common with the refractory material, preferably whereinthe component in common comprises alumina.

-   D16. The process of any of embodiments D1 to D15, further comprising    partially pre-oxidizing at least a portion of the collector alloy    from a raw state, wherein of the 100 parts by weight of the    collector alloy introduced in the converter feed to the pot, the    converter feed comprises at least 20 parts by weight of the    partially pre-oxidized collector alloy, preferably, wherein the    partial pre-oxidizing comprises passing particles of the raw    collector alloy through an oxygen-rich flame, preferably wherein the    flame exhibits a flame temperature of not less than 2000° C., more    preferably 2000° C. to 3500° C., and especially 2000° C. to 2800° C.-   D17. The process of any of embodiments D1 to D16, wherein the    converter feed further comprises the recycle slag in an amount of    from about 5 to 100 parts by weight per 100 parts by weight total of    the raw collector alloy and the partially pre-oxidized collector    alloy product of step (I) in the converter feed.-   D18. The process of any of embodiments D1 to D17, further comprising    the steps of:

(1) smelting a catalyst material in a (preferably non-converting)primary furnace;

(2) recovering a primary furnace slag and a first collector alloy fromthe primary furnace;

(3) smelting the primary furnace slag in a (preferably non-converting)secondary furnace, preferably with the addition of metallurgical coke;

(4) recovering a secondary furnace slag and a second collector alloyfrom the secondary furnace;

(5) wherein the first and/or second collector alloys are partiallypre-oxidized in step (I), and wherein the converter feed in step (II)comprises the first and/or second collector alloys and/or the partiallypre-oxidized collector alloy from step (I); and

(6) supplying at least a portion of the slag recovered from theconverter in step (d) to the secondary furnace for smelting with theprimary furnace slag in step (3).

-   D19. The process of any of embodiments D1 to D18, further    comprising:

(A) lining the pot with a refractory;

(B) holding the molten alloy pool in the refractory-lined pot;

(C) jacketing the pot; and

(D) circulating a coolant through the jacket.

-   D20. The process of any of embodiments D1 to D19, wherein the    converter comprises a rotary converter, wherein the rotary converter    comprises:

wherein the pot comprises an inclined pot mounted for rotation about alongitudinal axis;

a refractory lining in the pot for holding a molten alloy pool;

an opening in a top of the pot to introduce a converter feed into thepot with the alloy pool;

a lance for injecting oxygen-containing gas into the alloy pool;

a heat transfer jacket for the pot;

a coolant system to circulate a heat transfer medium through the jacket;and

a tap to recovery the slag and the alloy from the pot.

Integrated Converter Process for PGM Recovery and Enrichment

-   E1. A process for recovering and enriching PGM, comprising the steps    of:

(1) smelting a catalyst material in a (preferably non-converting)primary furnace;

(2) recovering a primary furnace slag and a first collector alloy fromthe primary furnace;

(3) smelting the primary furnace slag in a (preferably non-converting)secondary furnace;

(4) recovering a secondary furnace slag and a second collector alloyfrom the secondary furnace;

(5) converting the first and second collector alloys in a converter torecover PGM enriched alloy and slag; and

(6) supplying at least a portion of the slag recovered from theconverter in step (5) to the secondary furnace for smelting with theprimary furnace slag in step (3).

-   E2. The process of embodiment E1, wherein a pot of the converter is    lined with a refractory material, and further comprising supplying a    portion of the primary furnace slag from step (2) to the pot as a    refractory protectant.-   E3. The process of embodiment E2 wherein the refractory protectant    comprises no more than 20 parts by weight of the primary furnace    slag per 100 parts by weight of the total first and second collector    alloys supplied to the converter, preferably 18 parts by weight of    the primary furnace slag per 100 parts by weight of the total first    and second collector alloys supplied to the converter, more    preferably between 5 and 15 parts by weight of the primary furnace    slag per 100 parts by weight of the total first and second collector    alloys supplied to the converter.-   E4. The process of any of embodiments E1 to E3, wherein the    converting in step (5) is continued until an alloy pool in the pot    of the converter comprises no more than about 10 wt % iron,    preferably no more than 5 wt % iron, based on the total weight of    the alloy pool.-   E5. The process of embodiment E4, wherein the first and second    collector alloys supplied to the converter comprise:

from 0.5 to 12 wt % PGM;

no less than 40 wt % iron, preferably 40 to 80 wt % iron;

no less than 0.5 wt % nickel, preferably 1 to 15 wt % nickel;

no more than 3 wt % sulfur, preferably no less than 0.1 wt % sulfur;

preferably no more than 3 wt % copper, more preferably 0.1 to 3 wt %copper; and preferably no more than 20 wt % silicon, more preferably 1to 20 wt % silicon.

-   E6. The process of Embodiment E5, wherein the PGM-enriched alloy    recovered from step (5) comprises:

no less than 25 wt % PGM, preferably from 25 to 60 wt % PGM;

no less than 25 wt % nickel, preferably from 25 to 70 wt % nickel; and

preferably no more than 2 wt % silicon, no more than 5 wt % phosphorus,no more than 10 wt % copper, and no more than 2 wt % sulfur.

-   E7. The process of any of embodiments E1 to E6, wherein a feed to    the converter comprises:

(i) 100 parts by weight total of the first and second collector alloys;and

(ii) no more than 20 parts by weight of an added flux materialcomprising more than 10 weight percent silica and more than 10 weightpercent of calcium oxide, magnesium oxide, or a combination of calciumoxide and magnesium oxide, by weight of the added flux material.

-   E8. The process of any of embodiments E1 to E7, further comprising:

lining the pot with a refractory material; and

supplying a refractory protectant to the pot holding the alloy pool at arate up to 20 parts by weight refractory protectant per hundred parts byweight of the first and second collector alloys in the converter feed,preferably not more than 18 parts by weight per 100 parts by weight ofthe first and second collector alloys, and more preferably at a ratebetween 5 and 15 parts by weight refractory protectant per 100 parts byweight of the first and second collector alloys.

-   E9. The process of embodiment E8, wherein the refractory protectant    comprises a component in common with the refractory material,    preferably wherein the component in common comprises alumina.-   E10. The process of any of embodiments E1 to E9, further comprising    partially pre-oxidizing at least a portion of the first and/or    second collector alloys from a raw state, wherein a feed to the    converter comprises at least 20 parts by weight of the partially    pre-oxidized collector alloy per 100 parts by weight total converter    feed, preferably, wherein the partial pre-oxidizing comprises    passing particles of the collector alloy through an oxygen-rich    flame, preferably wherein the flame exhibits a flame temperature of    not less than 2000° C., more preferably 2000° C. to 3500° C., and    especially 2000° C. to 2800° C.-   E11. The process of any of embodiments E1 to E10, wherein a feed to    the converter comprises the first and second collector alloys and    further comprises a recycled portion of the converter slag from    step (6) in an amount of from about 5 to 100 parts by weight per 100    parts by weight total of the first and second collector alloys.-   E12. The process of any of embodiments E1 to E11, wherein the    converter has an operating cycle comprising the steps of:

(I) partially pre-oxidizing at least a portion of the first and/orsecond collector alloys;

(II) melting a charge of the partially pre-oxidized collector alloy fromstep (I) in the pot of the converter to form an alloy pool to start theconverter operating cycle;

(III) introducing a converter feed into the pot with the alloy pool,wherein the converter feed comprises: (i) partially pre-oxidizedcollector alloy product from step (I), (ii) the first and/or secondcollector alloys without pre-oxidation, or (iii) a combination thereof,wherein the converter feed may optionally further comprise recycle slagfrom step (5) of a previous converter cycle;

(IV) injecting oxygen-containing gas into the alloy pool for theconversion of the iron to iron oxide and the enrichment of the PGM inthe alloy pool;

(V) allowing the slag comprising the iron oxide to collect in thelow-density layer above the alloy pool;

(VI) terminating steps (III) and (IV) and tapping the low-density layerto recover the slag from the converter;

(VII) repeating a sequence of steps (III), (IV), (V), and (VI) aplurality of times, including one or more non-final sequences and afinal sequence, wherein step (VI) in each sequence follows steps (IV)and (V);

(VIII) prior to the tapping of the low-density layer in step (VI) ofeach non-final sequence, allowing alloy entrained in the low-densitylayer to substantially settle into the alloy pool following terminationof the oxygen-containing gas injection;

(IX) promptly commencing the tapping of the low-density layer followingtermination of the oxygen-containing gas injection in step (VI) in thefinal sequence wherein freezing of the alloy pool is avoided; and

(X) at an end of the converter cycle, tapping the alloy pool to recoverthe PGM-enriched alloy wherein freezing of the alloy pool is avoided.

-   E13. The process of any of embodiments E1 to E12, further    comprising:

(A) lining a pot of the converter with a refractory;

(B) holding a molten alloy pool in the refractory-lined pot;

(C) jacketing the pot; and

(D) circulating a coolant through the jacket.

-   E14. The process of any of embodiments E1 to E13, wherein the    converter comprises a rotary converter, wherein the rotary converter    comprises:

an inclined pot mounted for rotation about a longitudinal axis;

a refractory lining in the pot for holding a molten alloy pool;

an opening in a top of the pot to introduce a converter feed into thepot with the alloy pool;

a lance for injecting oxygen-containing gas into the alloy pool;

a heat transfer jacket for the pot;

a coolant system to circulate a heat transfer medium through the jacket;and

a tap to recovery the slag and the alloy from the pot.

Jacketed PGM Enrichment Converter

-   F1. A converting process, comprising:

(a) lining a pot of a rotary converter with a refractory;

(b) holding a molten alloy pool in the pot;

(c) introducing a converter feed into the pot with the alloy pool,wherein the converter feed comprises a collector alloy comprising iron(preferably comprising no less than 0.5 wt % PGM, no less than 40 wt %iron, and no less than 0.5 wt % nickel, based on the total weight of thecollector alloy;

(d) injecting oxygen-containing gas into the alloy pool to convert ironfrom the collector alloy to iron oxide and enrich PGM in the alloy pool;

(e) jacketing the pot;

(f) circulating a coolant through the jacket;

(g) allowing a slag comprising the iron oxide to collect in alow-density layer above the alloy pool;

(h) tapping the low-density layer to recover the slag from theconverter; and

(i) tapping the alloy pool to recover the PGM-enriched alloy.

-   F2. The process of embodiment F1, further comprising monitoring a    temperature of the refractory lining.-   F3. The process of embodiment F2, further comprising sensing the    temperature in the refractory lining with one or more sensors    mounted in the refractory lining, communicating temperature sensing    information from the one or more sensors to one or more    transmitters, and transmitting signals containing the temperature    sensing information from the one or more transmitters to a receiver.-   F4. The process of embodiment F3 wherein the one or more    transmitters are mounted externally on the pot and wirelessly    transmit the signals to the receiver.-   F5. A rotary converter for PGM enrichment of a collector alloy,    comprising:

an inclined converter pot mounted for rotation about a longitudinalaxis;

a refractory lining in the pot for holding a molten alloy pool;

an opening in a top of the pot to introduce a converter feed into thepot with the alloy pool;

a lance for injecting oxygen-containing gas into the alloy pool;

a heat transfer jacket for the pot;

a coolant system to circulate a heat transfer medium through the jacket;and

a tap to recovery slag and alloy from the pot.

-   F6. The rotary converter of embodiment F5, further comprising a    control system to adjust the coolant supply and oxygen injection    rate for maintaining a temperature in the alloy pool between    1250° C. and 1700° C., preferably 1450° C. to 1700° C.-   F7. The rotary converter of embodiment F5 or embodiment F6, further    comprising a shaft and a motor to drive the rotation of the pot.-   F8. The rotary converter of embodiment F7, further comprising a    rotary coupling to supply and return the heat transfer medium    through the shaft to and from the jacket.-   F9. The rotary converter of any of embodiments F5 to F8, further    comprising radially spaced temperature sensors mounted in the    refractory lining in communication with one or more transmitters to    transmit signals containing temperature sensing information to a    receiver.-   F10. The rotary converter of embodiment F9, wherein the temperature    sensors are mounted adjacent a metal wall of the pot.-   F11. The rotary converter of embodiment F10, wherein the one or more    transmitters are mounted externally on the pot and wirelessly    transmit the signals to the receiver.-   F12. The rotary converter of any of embodiments F5 to F11, further    comprising a fume hood adjacent the opening of the pot.-   F13. The rotary converter of any of embodiments F5 to F12, further    comprising a burner to heat the pot, preferably wherein the burner    is a water cooled oxy-fuel burner.-   F14. The rotary converter of any of embodiments F5 to F13, wherein    the burner comprises a chute to introduce converter feed into a    flame of the burner.-   F15. The rotary converter of any of embodiments F5 to F14, further    comprising a water cooled heat shield adjacent the opening in the    pot.-   F16. The rotary converter of any of embodiments F5 to F15, wherein    the refractory lining comprises an alumina based ramming refractory.-   F17. The rotary converter of any of embodiments F5 to F16, further    comprising a feed system, preferably comprising a hopper and a    vibrating feeder, to supply the converter feed through the opening    into the pot.-   F18. The rotary converter of embodiment F17, further comprising a    charge of the converter feed in the feed system.-   F19. The rotary converter of embodiment F18, wherein the converter    feed comprises a collector alloy comprising no less than 0.5 wt %    PGM, no less than 40 wt % iron, and no less than 0.5 wt % nickel,    based on the total weight of the collector alloy.-   F20. The rotary converter of embodiment F19, wherein the converter    feed further comprises recycle converter slag.

EXAMPLES

In the following examples, process 200 according to FIG. 8 was used.Catalyst material 202 was smelted in electric arc furnace 204 having anominal capacity of 907 kg/h (1 tph), a transformer rated at 1.2 MVA,with a secondary voltage of 180 V and a secondary current of 2700 A.Slag 205, comprising mainly aluminosilicate, was recovered from thefurnace 204, granulated in water in granulator 206, dried in rotary kiln208, and repackaged in bag-filling station 210. The PGM collector alloy211 was cast into molds 212, solidified, and crushed in crusher 214 to−4 mesh (− 3/16 in.).

The dried slag 210 from the primary furnace 204 was smelted in second,finishing electric arc furnace 218 having a nominal capacity of 907 kg/h(1 tph), a transformer rated at 1.2 MVA, with a secondary voltage of 180V and a secondary current of 2700 A. Slag 219 recovered from the furnace218 was granulated in granulator 220 and recycled in step 222 for anappropriate use, e.g., as aggregate. The PGM collector alloy 223 fromthe secondary furnace 218 was cast into molds 224, solidified, andcrushed in crusher 214 to −1.9 cm (¾ in.).

A charge of partially pre-oxidized PGM collector alloy 184 was preparedfrom collector alloy 211 and/or 223 as described in the example. Thepre-oxidized alloy 184 was placed in the pot 232 of a water-cooled TBRC227 lined with an alumina-based ramming refractory, and melted with agas burner 228 to a temperature of at least 1450° C. The pre-oxidizedalloy pool was sufficient to inject oxygen below the surface of thealloy pool, generally filling about 10-20% of the available volume ofthe pot 232. A portion of the aluminosilicate slag 210 from the primaryfurnace 204 was placed on top of the alloy pool as refractory protectant233 at the start of each oxygen injection cycle. Unless otherwisestated, the total amount of protectant 233 used for each TBRC operatingcycle was 60-80 kg (132-176 lbs), apportioned between oxygen injectioncycles, e.g., following the initial alloy pool melt and each non-finalslag tapping.

While the pot 232 was rotated, the burner 228 was shut off and oxygen234 was injected into the alloy pool using lance 229 at a rate tomaintain a temperature sufficient to avoid solidification of the alloypool but at a sufficient rate to maintain the temperature in the alloypool no higher than 1700° C., e.g., 1450° C. to 1700° C., whilecirculating cooling water through the TBRC jacket. Unless otherwisenoted the oxygen injection rate was 58 Nm³/h (36 SCFM). The PGMcollector alloy 211, 223 from the furnaces 204, 218 (966 kg unlessotherwise noted) and recycle slag 254, 258 (359 kg unless otherwisenoted) that had been placed in hopper 225 was fed into the pot 232 viavibrating feeder 226 at a generally steady rate of 210 kg/h, except whenstopped during slag tappings, unless otherwise noted. The pot 232 filledas slag was formed and the alloy pool grown by the feed into the pot232. When the volume of the pot 232 was filled sufficiently, the potrotation, oxygen injection, and alloy feed were stopped. After waitingseveral minutes to allow phase separation and alloy disentrainment fromthe slag layer, slag 242 was tapped into molds 244 by tipping the pot232, taking care to avoid tapping any of the alloy phase, erring on theside of leaving some slag on the top of the alloy phase.

The oxygen injection and alloy feed into the remaining alloy pool werethen resumed until the pot 232 was again filled, and slag 242 tapped asdescribed above. The cycle was repeated several times until the alloypool had grown to a desired volume for tapping. The final slag tappingjust before tapping the alloy was performed promptly after stopping theoxygen injection and collector alloy feed, taking care thatsubstantially all of the slag 242 was tapped, erring on the side ofalloy entrainment in the slag. The PGM-enriched alloy 245 was thentapped into ingot molds 246, cooled, and solidified.

After the slag molds 244 were cooled, the solidified slag 248 was fedthrough slag crusher 250 and magnetic separator 252. The non-magneticfractions from the final slag tapping and the earlier tappings weresorted into containers 254 and 256, respectively. The non-magneticfraction 256 was smelted in the secondary furnace 218 with the slag 210from the primary furnace. The magnetic fractions 258 from all of theconverter slag and the non-magnetic fraction 254 from the final slagtapping were placed in the feed hopper 225 with collector alloy 211and/or 223 for a subsequent TBRC batch. The same result would haveobtained if the entirety of the final slag tapping were placed directlyin the hopper 238, bypassing the magnetic separator 252.Assays reportedbelow were determined using a combination of inductively coupled plasmaspectroscopy (ICP) and desktop X-ray fluorescence (XRF). Unlessotherwise noted, typical assays are reported below.

Example 1: Smelting catalyst material in primary furnace. In thisexample, catalyst material from automotive catalytic converters issmelted in the electric arc furnace 204. Iron oxide is added as neededto provide a minimum iron content in the feed of at least 1 wt %, basedon the total weight of the feed to the furnace 204. Lime (CaO) is addedin an amount of 2.5 wt %. After smelting, 72.5 tonne slag and 2500 kgcollector alloy are typically recovered, cooled, and solidified. Thecollector alloy and slag have the following typical assays set out inTables 1 and 2.

Example 2: Smelting slags in secondary furnace. In this example, 99.79tonne (110 t) of the Example 1 slag from the primary furnace 204 and9979 kg (11 t) of non-magnetic converter slag 256 from Example 5 (Table13 below) are smelted in the furnace 218. Metallurgical grade coke isadded in an amount of 0.5 wt %. After smelting, 104.33 tonne (115 t)slag and 3000 kg collector alloy are recovered, cooled, and solidified.The collector alloy and slag have the typical assays set out in Tables 3and 4.

Example 3: Pre-oxidation of collector alloy—starter alloy. In thisexample, 150 kg of a starter alloy from a previous starter alloypreparation cycle were loaded into the TBRC and melted after 30 minusing the burner 228. The beginning starter alloy has the typical assayshown in Table 5. The collector alloy (1250 kg) from Example 1 (Table1), recycle slag (200 kg, or [200/(150+1250)]*100=14.2 parts recycleslag per hundred collector alloy), and refractory protectant (100 kg, or[100/(150+1250)]*100=7.1 parts protectant per hundred collector alloy)were supplied to the TBRC. The refractory protectant was the furnaceslag from Example 1 (Table 2). The recycle slag has the typical assay asshown in Table 6.

The oxygen injection rate during the converting was 37 Nm³/h 23 SCFM),and the slag was tapped several times, after waiting for several minutesto allow alloy disentrainment. The final slag tapping was done in thesame way, which it is noted is different from the usual converter cycleto produce PGM-enriched alloy product where slag contamination of thealloy is minimized. After 6 h of oxygen injection, corresponding to 44%oxidation, the alloy was tapped, solidified, and crushed for use as thestarter alloy in subsequent TBRC converting cycles. The product starteralloy has the typical assay as shown in Table 7.

Example 4: Converting with starter alloy. In this example, 158 kg of thestarter alloy produced from Example 3 (Table 7) were loaded into theTBRC and melted after 30 min using the burner 228. The converter feedwas made up of collector alloy (966 kg) from Example 1 (Table 1), andthe recycle slag (358 kg, or [358/(158+966)]*100=32 parts recycle slagper hundred collector alloy) used in Example 3 (Table 6). Refractoryprotectant (60 kg) supplied to the TBRC was the furnace slag fromExample 1 (Table 1), or [60/(158+966)]*100=5.3 parts protectant perhundred collector alloy. The oxygen injection rate during the convertingwas 37 Nm³/h (23 SCFM), and the slag was tapped several times as needed,after waiting for several minutes each time to allow alloydisentrainment. The final slag tapping was started within 5 minutes ofstopping oxygen injection without waiting for complete alloydisentrainment. After 10 h of oxygen injection, corresponding to 99%iron conversion, the alloy was tapped and formed into ingots. ThePGM-enriched alloy (247.45 kg) has the typical assay as shown in Table8.

The slag tappings were cooled, solidified, crushed, milled, andmagnetically separated. The magnetically susceptible fraction wascollected and combined with the non-magnetic fraction of the final slagtapping (354 kg total) for use as recycle slag in a subsequentconverting cycle. The non-magnetic fraction of the non-final slagtappings were collected (1963 kg total) for smelting in the secondaryfurnace similarly to example 2. The recycle slag and smelting slag havethe typical assays shown in Tables 9 and 10:

This example shows that PGM collector alloy can be enriched with a highoxygen injection rate without a large amount of added flux materials,using only recycle converter slag from a previous cycle and primaryfurnace slag as a refractory protectant. This example demonstrates theuse of partially pre-oxidized starter alloy to reduce the TBRC cycleoperation time and improve PGM enrichment. This example alsodemonstrates the feasibility of converting PGM collector alloy using awater-cooled, jacketed TBRC.

Example 5: Converting with flame pre-oxidized collector alloy. In thisexample, 590 kg of collector alloy were flame pre-oxidized using theburner 228. The collector alloy was loaded into the hopper forpre-oxidation during a night shift. The two-burner assembly 228 was setat 0.48 MMBtu/h each (0.96 MMBtu/h total) with 20% excess oxygen toproduce a flame temperature greater than 2000° C. The collector alloywas fed into the TBRC using an apparatus similar to that shown in FIG.2C so that the particles passed through the flame and fell into theTBRC, forming a coating on the refractory. The next morning, thepre-oxidized collector alloy was melted after 30 min by increasing thefiring rate of the burners to 1.1 MMIBtu/h total.

Next, the converter feed was made up of collector alloy (700 kg) fromExample 1 (Table 1), and recycle slag (416 kg, or [416/(590+700)]*100=32parts recycle slag per hundred collector alloy) produced from Example 4(Table 9). The refractory protectant (80 kg) was furnace slag fromExample 1 (Table 2), or [80/(590+700)]*100=6.2 parts protectant perhundred collector alloy. The oxygen injection rate during the convertingwas 46 Nm³/h (29 SCFM), and the slag was tapped several times as needed,after waiting each time for several minutes to allow alloydisentrainment. The final slag tapping was started within 5 minutes ofstopping oxygen injection without waiting for complete alloydisentrainment. After 9 h of oxygen injection, corresponding to 99% ironconversion, the alloy was tapped and formed into ingots. ThePGM-enriched alloy (218.71 kg) has the typical assay as shown in Table11.

The slag tappings were cooled, solidified, crushed, milled, andmagnetically separated. The magnetically susceptible fraction wascollected and combined with the non-magnetic fraction of the final slagtapping (588 kg total) for use as recycle slag in a subsequentconverting cycle. The non-magnetic fraction of the non-final slagtappings was collected (1772 kg total) for smelting in the secondaryfurnace (see Example 2). The recycle slag and smelting slag have thetypical assays shown in Tables 12 and 13.

This example shows that partial pre-oxidation by flame oxidation ofcollector alloy, relative to Example 4, allows a larger quantity of thecollector alloy to be processed in the TBRC with higher oxygen injectionrates and a shorter cycle time to obtain a higher purity of enriched PGMalloy.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe following claims. It is the express intention of the applicant notto invoke 35 U.S.C. § 112(f) for any limitations of any of the claimsherein, except for those in which the claim expressly uses the words‘means for’ together with an associated function and without anyrecitation of structure. The priority document is incorporated herein byreference.

TABLE 1 Primary furnace collector alloy composition (Example 1)Component Wt % Fe 55 PGM 8 Ni 10 Si 10 P 10 Cu 1.0 S 0.4 Cr 1.5 Ti 1.5Other 2.6 TOTAL 100

TABLE 2 Primary furnace slag assay (Example 1) Component Wt % MgO 8 CaO2.5 Al₂O₃ 36 SiO₂ 36 S 0.5 FeO 3 NiO 0.1 P2O₅ 0.7 Cr₂O₃ 0.15 TiO₂ 0.6PGM 0.08 Ce₂O₃ 4 ZrO₂ 4 Other 4.5 TOTAL 100

TABLE 3 Secondary furnace collector alloy assay (Example 2) Component Wt% Fe 75 PGM 0.8 Ni 3 Si 5 P 10 Cu 0.5 S 0.5 Cr 0.6 Ti 0.15 Other 4.5TOTAL 100

TABLE 4 Secondary furnace slag assay (Example 2) Component Wt % MgO 8CaO 2.5 Al₂O₃ 38 SiO₂ 38 S 0.1 FeO 1.9 NiO 0.1 P2O₅ 0.7 Cr₂O₃ 0.1 TiO₂0.4 PGM 0.003 Ce₂O₃ 4 ZrO₂ 4 Other 2.2 TOTAL 100

TABLE 5 Previous starter alloy assay (Example 3) Component Wt % Fe 60.7PGM 12 Ni 15.0 Si 0.05 P 9.6 Cu 0.4 S 0.5 Cr 0.01 Ti 0.01 Other 1.7TOTAL 100

TABLE 6 Converter recycle slag feed composition (Example 3) Component Wt% MgO 0.5 CaO 0.6 SiO₂ 12.2 Co₂O₃ 0.3 Al₂O₃ 12.5 FeO 55.4 NiO 9.4 P₂O₅5.8 Cr₂O₃ 0.06 TiO₂ 0.05 PGM 0.2 Other 3.0 TOTAL 100

TABLE 7 Product starter alloy assay (Example 3) Component Wt % Fe 52.3PGM 10.1 Ni 24.7 Si 0.5 P 7.3 Cu 2.1 S 0.4 Cr 0.01 Ti 0.01 Other 2.5TOTAL 100

TABLE 8 PGM enriched alloy assay (Example 4) Component Wt % Fe 2.6 PGM34 Ni 56.1 Si 0.01 P 1.2 Cu 3.5 S 0.2 Other 2.4 TOTAL 100

TABLE 9 High grade converter slag product assay (Example 4) Component Wt% MgO 0.1 CaO 0.1 SiO₂ 10.0 Co₂O₃ 0.4 Al₂O₃ 10.5 FeO 57.4 NiO 12.6 P2O₅7.4 Cr₂O₃ 0.06 TiO₂ 0.05 PGM 0.21 Other 1.2 TOTAL 100

TABLE 10 Low grade converter slag product assay (Example 4) Component Wt% MgO 0.5 CaO 0.6 SiO₂ 27.2 Co₂O₃ 0.01 Al₂O₃ 10.5 FeO 39.4 NiO 0.4 P2O₅15.8 Cr₂O₃ 1.6 TiO₂ 1.5 PGM 0.08 Other 2.4 TOTAL 100

TABLE 11 PGM enriched alloy assay (Example 5) Component Wt % Fe 3.2 PGM41.2 Ni 48.7 Si 0.01 P 0.9 Cu 5.2 S 0.3 Other 0.5 TOTAL 100

TABLE 12 High grade converter slag product composition (Example 5)Component Wt % MgO 0.1 CaO 0.1 SiO₂ 9.6 Co₂O₃ 0.6 Al₂O₃ 9.5 FeO 57.4 NiO14.2 P2O₅ 5.4 Cr₂O₃ 0.01 TiO₂ 0.01 PGM 0.2 Other 2.9 TOTAL 100

TABLE 13 Low grade converter slag product composition (Example 5)Component Wt % MgO 0.5 CaO 0.6 SiO₂ 32.2 Co₂O₃ 0.01 Al₂O₃ 9.5 FeO 39.4NiO 0.5 P2O₅ 9.8 Cr₂O₃ 2.5 TiO₂ 1.8 PGM 0.08 Other 3.1 TOTAL 100

What is claimed is:
 1. A process for converting platinum group metal(PGM) collector alloy, comprising the steps of: (a) introducing aconverter feed into a pot of a converter holding a molten alloy pool,wherein the converter feed comprises: (i) 100 parts by weight of acollector alloy comprising no less than 0.5 wt % PGM, no less than 40 wt% iron, and no less than 0.5 wt % nickel, based on the total weight ofthe collector alloy; and (ii) if an added flux material comprises morethan 10 weight percent silica and more than 10 weight percent of calciumoxide, magnesium oxide, or a combination of calcium oxide and magnesiumoxide, by weight of the added flux material, no more than 20 parts byweight of the added flux material; (b) injecting oxygen-containing gasinto the alloy pool to convert iron and one or more other oxidizableelements from the collector alloy to the corresponding oxides and enrichPGM in the alloy pool; (c) allowing a slag comprising the iron oxide tocollect in a low-density layer above the alloy pool; (d) tapping thelow-density layer to recover the slag from the converter; and (e)tapping the alloy pool to recover the PGM-enriched alloy.
 2. The processof claim 1, further comprising: lining the pot with a refractorymaterial; and supplying a refractory protectant to the pot holding thealloy pool at a rate up to 20 parts by weight refractory protectant perhundred parts by weight of the collector alloy in the converter feed,preferably not more than 18 parts by weight per 100 parts by weight ofthe collector alloy, and more preferably at a rate between 5 and 15parts by weight refractory protectant per 100 parts by weight of thecollector alloy.
 3. The process of claim 2, wherein the refractoryprotectant is supplied to the pot (i) after initially melting the alloypool and prior to commencing step (b), (ii) during one or both of steps(a) and (b), and/or (iii) after stopping one or both of steps (a) and(b) to tap the low-density layer in step (d), prior to resuming said oneor both of steps (a) and (b).
 4. The process of claim 2, wherein therefractory protectant is supplied to the pot together with the collectoralloy introduced in step (a).
 5. The process of claim 2, wherein therefractory protectant is supplied to the pot separately from thecollector alloy introduced in step (a), preferably wherein the supply ofrefractory protectant to the pot is periodic.
 6. The process of claim 2,wherein the refractory protectant comprises a component in common withthe refractory material, preferably wherein the component in commoncomprises alumina.
 7. The process of claim 6, further comprisinginjecting the oxygen-containing gas into the alloy pool in step (b)through a lance extended into the alloy pool, wherein the lancecomprises a consumable refractory material and is advanced into the poolas a tip of the lance is consumed, wherein the consumable refractorymaterial comprises a component in common with the lining, preferablywherein the component in common comprises alumina.
 8. The process ofclaim 2, wherein the refractory material of the lining comprises aramming refractory comprising alumina, preferably wherein the rammingrefractory comprises at least 90 wt % alumina.
 9. The process of claim2, further comprising: sensing temperature in the refractory lining withradially spaced sensors mounted in the refractory lining; communicatingtemperature sensing information from the sensors to one or moretransmitters; and transmitting signals containing the temperaturesensing information from the one or more transmitters to a receiver;preferably wherein the sensors are mounted adjacent a metal wall of thepot and/or the one or more transmitters are mounted externally on thepot and wirelessly transmit the signals to the receiver.
 10. The processof claim 2, further comprising jacketing the pot and circulating acoolant, preferably water, through the jacket during step (b).
 11. Theprocess of claim 2, wherein the oxygen-containing gas is injected intothe converter alloy pool at a sufficient rate to maintain the alloy poolin a molten state at a temperature no higher than 1800° C., preferablyat a temperature in a range from about 1250° C. to 1700° C., morepreferably 1450° C. to 1700° C.
 12. The process of claim 1, furthercomprising, prior to step (a), the step of (I) partially pre-oxidizingat least a portion of the collector alloy from a raw state, preferablywherein the partial pre-oxidation in step (I) comprises from 10 to 90percent conversion of iron, more preferably from 25 to 75 percent ironconversion, and even more preferably from 30 to 60 percent ironconversion, based on the iron in the raw collector alloy portion priorto step (I).
 13. The process of claim 12, wherein the pre-oxidizing instep (I) comprises (I.A) passing particles of the raw collector alloythrough an oxygen-rich flame, preferably wherein the flame exhibits aflame temperature of not less than 2000° C., more preferably 2000° C. to3500° C., and especially 2000° C. to 2800° C.
 14. The process of claim13, wherein the oxygen rich flame is produced by a burner for heatingthe pot, and further comprising (I.B) depositing at least partiallymelted and/or pre-oxidized collector alloy particles from the flame intothe pot.
 15. The process of claim 14, further comprising the steps of:(I.C) cooling and solidifying the particles to form a coating of thepre-oxidized collector alloy on an interior surface of a refractorylining of the pot; (II) melting the coating in the pot to form asufficient volume of the alloy pool for the injection of theoxygen-containing gas in step (b); and (III) then commencing theconverter feed introduction into the pot in step (a) and theoxygen-containing gas injection into the alloy pool in step (b).
 16. Theprocess of claim 12, further comprising the steps of: (II) melting thepartially pre-oxidized collector alloy in the pot to form a sufficientvolume of the alloy pool for the injection of the oxygen-containing gasin step (b); and (III) then commencing the converter feed introductioninto the pot in step (a) and the oxygen-containing gas injection intothe alloy pool in step (b).
 17. The process of claim 16, wherein thepre-oxidizing in step (I) comprises operating the converter through acycle of steps (II), (III), (a), (b), (c), (d), and (e) to prepare apartially oxidized starter alloy, wherein the starter alloy preparationcycle comprises: melting a previously prepared charge of the partiallyoxidized starter alloy in the emptied pot to form the alloy pool;periodically or continuously supplying the converter feed to the alloypool in step (a) concurrently with the injection of theoxygen-containing gas in step (b); continuing the injection of theoxygen-containing gas to partially oxidize the alloy pool, preferablywherein from 10 to 90 percent, more preferably from 25 to 75 percent, ofiron in the converter feed is oxidized, based on the weight of iron inthe converter feed supplied to the converter alloy pool; tapping theslag from the converter pot, preferably a plurality of times; thenrecovering and solidifying the partially oxidized alloy pool; andpreferably dividing the solidified, partially oxidized collector alloyfrom the starter alloy preparation cycle into a plurality of starteralloy charges for a like plurality of converter operating cycles and/orstarter alloy preparation cycles.
 18. The process of claim 12, whereinthe pre-oxidizing in step (I) comprises contacting particles of the rawcollector alloy with an oxygen-containing gas at a temperature above800° C., preferably between 800° C. and 950° C., preferably in a rotarykiln or fluidized bed roaster.
 19. The process of claim 1, furthercomprising the steps of: (A.1) separating the slag recovered in step (d)into a plurality of portions; (A.2) recycling a first one of therecovered slag portions from step (A.1) to the converter feed introducedto the pot in step (a), wherein the converter feed comprises therecycled slag in an amount of from about 5 to 100 parts by weight per100 parts by weight of the collector alloy, preferably wherein theconverter feed comprises the recycled slag in an amount of from 10 to 50parts by weight per 100 parts by weight of the collector alloy.
 20. Theprocess of claim 19, further comprising (A.3) combining the collectoralloy and the recycle slag for concurrent introduction in the converterfeed in step (a), preferably from a single feed unit.
 21. The process ofclaim 19, wherein the recycled slag in step (A.2) comprises a high-gradeportion of the recovered slag from step (d) having a higher PGM contentthan an average overall PGM content of the recovered slag from step (d)and/or a nickel content greater than about 2 percent by weight of therecycled slag.
 22. The process of claim 21, further comprising the stepsof: (B.1) cooling, solidifying, and crushing the recovered slag fromstep (d); (B.2) magnetically separating the crushed slag into amagnetically susceptible fraction and a non-magnetically susceptiblefraction; (B.3) recycling the magnetically susceptible fraction to theconverter feed in step (A.2); and (B.4) optionally recycling a portionof the non-magnetically susceptible fraction to the converter feed instep (A.2).
 23. The process of claim 22, further comprising the stepsof: (C.1) prior to steps (a) to (e), beginning a converter operationcycle by melting a partially pre-oxidized collector alloy in the pot toform the alloy pool; (C.2) then, prior to step (e), repeating a sequenceof steps (a), (b), (c), and (d) a plurality of times, wherein step (d)in each sequence follows steps (b) and (c); (C.3) recycling the slagrecovered from a final tapping of the low-density layer in step (d) in alast one of the sequences of step (C.2) to the converter feed in step(A.2) regardless of magnetic susceptibility, and/or recycling all orpart of the non-magnetically susceptible fraction separated in step(B.2) from the final tapping in step (d) to the converter feed in step(A.2); and (C.4) after the final tapping of the low-density layer instep (d) in the last one of the sequences of step (C.2), tapping thealloy pool in step (e).
 24. The process of claim 23, further comprisingthe steps of: (D.1) for the tapping(s) of the low-density layerpreceding the final tapping in step (C.2), allowing alloy entrained inthe low-density layer to substantially settle into the alloy pool beforethe tapping of the respective low-density layer(s); and (D.2) for thefinal tapping in step (C.2), quickly commencing the tapping to avoidfreezing of the alloy pool, optionally resulting in entrainment of alloyin the low-density layer for the final tapping in step (C.2).
 25. Theprocess of claim 1, further comprising the steps of: (1) prior to steps(a) to (e), beginning a converter operation cycle by melting a partiallypre-oxidized collector alloy in the pot to form the alloy pool for step(a); (2) then, prior to step (e), repeating a sequence of steps (a),(b), (c), and (d) a plurality of times, wherein step (d) in eachsequence follows steps (b) and (c); (3) for the tapping(s) of thelow-density layer in step (d) in each sequence of step (2) preceding afinal tapping of the low-density layer in step (d) in a final sequenceof step (2), allowing alloy entrained in the low-density layer tosubstantially settle into the alloy pool before the tapping of therespective low-density layer(s), preferably for a period of no less than5 minutes, following termination of the oxygen-containing gas injectionin the respective step (b) of the respective sequence of step (2); (4)for the final tapping of the low-density layer in the step (d) of thefinal sequence of step (2), starting the final tapping of thelow-density layer in step (d) within a period of no more than 5 minutesfollowing termination of the oxygen-containing gas injection in step (b)of the final sequence of step (2), optionally entraining alloy in thelow-density layer of the final tapping in step (d) of the final sequenceof step (2); and (5) after the final tapping of the low-density layer instep (d) in the last one of the sequences of step (2), tapping the alloypool in step (e).
 26. The process of claim 25, further comprising thesteps of: (6) cooling, solidifying, and comminuting the recovered slagfrom step (d) in each sequence of step (2); and (7) recycling the slagrecovered from the final tapping of the low-density layer in step (d) inthe final sequences of step (2) to the converter feed in step (a). 27.The process of claim 1, further comprising the steps of: (E.1) smeltinga catalyst material in a primary furnace; (E.2) recovering a primaryfurnace slag and a first collector alloy from the primary furnace; (E.3)smelting the primary furnace slag in a secondary furnace; (E.4)recovering a secondary furnace slag and a second collector alloy fromthe secondary furnace; (E.5) supplying the first and second collectoralloys to converter feed in step (a); and (E.6) supplying at least aportion of the slag recovered from the converter in step (d) to thesecondary furnace for smelting with the primary furnace slag in step(E.3).
 28. The process of claim 27, wherein the pot of the converter islined with a refractory material, and further comprising supplying aportion of the primary furnace slag from step (E.2) to the pot as arefractory protectant for steps (a) and (b), preferably at a rate notmore than 20 parts by weight of the primary furnace slag per 100 partsby weight of the collector alloy, more preferably 18 parts by weight ofthe primary furnace slag per 100 parts by weight of the collector alloy,more preferably at a rate between 5 and 15 parts by weight of theprimary furnace slag per 100 parts by weight of the collector alloy. 29.The process of claim 1, wherein the oxygen-containing gas injection instep (b) is continued until the alloy pool comprises no more than about10 wt % iron, preferably no more than 5 wt % iron, based on the totalweight of the alloy pool.
 30. The process of claim 29, wherein thecollector alloy comprises: from 0.5 to 12 wt % PGM; no less than 40 wt %iron, preferably 40 to 80 wt % iron; no less than 0.5 wt % nickel,preferably 1 to 15 wt % nickel; no more than 3 wt % sulfur, preferablyno less than 0.1 wt % sulfur; preferably no more than 3 wt % copper,more preferably 0.1 to 3 wt % copper; and preferably no more than 20 wt% silicon, more preferably 1 to 20 wt % silicon; and/or wherein thePGM-enriched alloy comprises: no less than 25 wt % PGM, preferably from25 to 60 wt % PGM; no less than 25 wt % nickel, preferably from 25 to 70wt % nickel; and preferably no more than 2 wt % silicon, no more than 2wt % phosphorus, no more than 10 wt % copper, and no more than 2 wt %sulfur.